|
Software synthesizers offer great power and versatility, but some players feel that division of attention between a MIDI keyboard and a computer keyboard and mouse robs some of the immediacy from the playing experience.[81] Devices dedicated to real-time MIDI control provide an ergonomic benefit, and can provide a greater sense of connection with the instrument than can an interface that is accessed through a mouse or a push-button digital menu. Controllers may be general-purpose devices that are designed to work with a variety of equipment, or they may be designed to work with a specific piece of software. Examples of the latter include Akai's APC40 controller for Ableton Live, and Korg's MS-20ic controller that is a reproduction of their MS-20 analog synthesizer. The MS-20ic controller includes patch cables that can be used to control signal routing in their virtual reproduction of the MS-20 synthesizer, and can also control third-party devices.[82] Control surfaces Control surfaces are hardware devices that provide a variety of controls that transmit real-time controller messages. These enable software instruments to be programmed without the discomfort of excessive mouse movements,[83] or adjustment of hardware devices without the need to step through layered menus. Buttons, sliders, and knobs are the most common controllers provided, but rotary encoders, transport controls, joysticks, ribbon controllers, vector touchpads in the style of Korg's Kaoss pad, and optical controllers such as Roland's D-Beam may also be present. Control surfaces may be used for mixing, sequencer automation, turntablism, and lighting control.[83] Specialized real-time controllers Audio control surfaces often resemble mixing consoles in appearance, and enable a level of hands-on control for changing parameters such as sound levels and effects applied to individual tracks of a multitrack recording or live performance output. MIDI footswitches are commonly used to send MIDI program change commands to effects devices, but may be combined with pedals in a pedalboard that allows detailed programming of effects units. Pedals are available in the form of on/off switches, either momentary or latching, or as "rocker" pedals whose position determines the value of a MIDI continuous controller. Drawbar controllers are for use with MIDI and virtual organs. Along with a set of drawbars for timbre control, they may provide controls for standard organ effects such as rotating speaker speed, vibrato and chorus.[84] Instruments A General MIDI sound module. A sound module, which requires an external controller to trigger its sounds. These devices are highly portable, but their limited programming interface requires computer-based tools for comfortable access to their sound parameters. A MIDI instrument contains ports to send and receive MIDI signals, a CPU to process those signals, an interface that allows user programming, audio circuitry to generate sound, and controllers. The operating system and factory sounds are often stored in a Read-only memory (ROM) unit.[2]:67–70 A MIDI Instrument can also be a stand alone module (without a piano style keyboard) consisting of a General MIDI soundboard (GM, GS and/XG), onboard editing, including transposing/pitch changes, MIDI instrument changes and adjusting volume, pan, reverb levels and other MIDI controllers. Typically, the MIDI Module will include a large screen, enabling the user to view information depending on the function selected at that time. Features can include scrolling lyrics, usually embedded in a MIDI File or Karaoke MIDI, playlists, song library and editing screens. Some MIDI Modules include a Harmonizer and the ability to playback and transpose MP3 audio files. Synthesizers Main article: Synthesizer Synthesizers may employ any of a variety of sound generation techniques. They may include an integrated keyboard, or may exist as "sound modules" or "expanders" that generate sounds when triggered by an external controller. Sound modules are typically designed to be mounted in a 19-inch rack.[2]:70–72 Manufacturers commonly produce a synthesizer in both standalone and rack-mounted versions, and often offer the keyboard version in a variety of sizes. Samplers Main article: Sampler (musical instrument) A sampler can record and digitize audio, store it in random-access memory (RAM), and play it back. Samplers typically allow a user to edit a sample and save it to a hard disk, apply effects to it, and shape it with the same tools that synthesizers use. They also may be available in either keyboard or rack-mounted form.[2]:74–8 Instruments that generate sounds through sample playback, but have no recording capabilities, are known as "ROMplers". Samplers did not become established as viable MIDI instruments as quickly as synthesizers did, due to the expense of memory and processing power at the time.[5]:295 The first low-cost MIDI sampler was the Ensoniq Mirage, introduced in 1984.[5]:304 MIDI samplers are typically limited by displays that are too small to use to edit sampled waveforms, although some can be connected to a computer monitor.[5]:305 Drum machines Main article: Drum machine Drum machines typically are sample playback devices that specialize in drum and percussion sounds. They commonly contain a sequencer that allows the creation of drum patterns, and allows them to be arranged into a song. There often are multiple audio outputs, so that each sound or group of sounds can be routed to a separate output. The individual drum voices may be playable from another MIDI instrument, or from a sequencer.[2]:84 Workstations and hardware sequencers Main articles: Music workstation and Music sequencer A button matrix MIDI controller Yamaha's Tenori-on controller allows arrangements to be built by "drawing" on its array of lighted buttons. The resulting arrangements can be played back using its internal sounds or external sound sources, or recorded in a computer-based sequencer. Sequencer technology predates MIDI. Analog sequencers use CV/Gate signals to control pre-MIDI analog synthesizers. MIDI sequencers typically are operated by transport features modeled after those of tape decks. They are capable of recording MIDI performances, and arranging them into individual tracks along a multitrack recording concept. Music workstations combine controller keyboards with an internal sound generator and a sequencer. These can be used to build complete arrangements and play them back using their own internal sounds, and function as self-contained music production studios. They commonly include file storage and transfer capabilities.[2]:103–4 Effects devices Main article: Effects unit Audio effects units that are frequently used in stage and recording, such as reverbs, delays and choruses, can be remotely adjusted via MIDI signals. Some units allow only a limited number of parameters to be controlled this way, but most will respond to program change messages. The Eventide H3000 Ultra-harmonizer is an example of a unit that allows such extensive MIDI control that it is playable as a synthesizer.[5]:322 Technical specifications [icon] This section requires expansion. (December 2013) MIDI messages are made up of 8-bit words (commonly called bytes) that are transmitted serially at 31.25 kilobaud. This rate was chosen because it is an exact division of 1 MHz, the speed at which many early microprocessors operated.[5]:286 The first bit of each word identifies whether the word is a status byte or a data byte, and is followed by seven bits of information.[2]:13–14 A start bit and a stop bit are added to each byte for framing purposes, so a MIDI byte requires ten bits for transmission.[5]:286 A MIDI link can carry sixteen independent channels of information. The channels are numbered 1-16, but their actual corresponding binary encoding is 0-15. A device can be configured to only listen to specific channels and to ignore the messages sent on other channels (“Omni Off” mode), or it can listen to all channels, effectively ignoring the channel address (“Omni On”). An individual device may be monophonic (the start of a new “note-on” MIDI command implies the termination of the previous note), or polyphonic (multiple notes may be sounding at once, until the polyphony limit of the instrument is reached, or the notes reach the end of their decay envelope, or explicit “note-off” MIDI commands are received). Receiving devices can typically be set to all four combinations of “omni off/on” versus “mono/poly” modes.[2]:14–18 Messages A MIDI message is an instruction that controls some aspect of the receiving device. A MIDI message consists of a status byte, which indicates the type of the message, followed by up to two data bytes that contain the parameters.[19] MIDI messages can be "channel messages", which are sent on only one of the 16 channels and can be heard only by devices receiving on that channel, or "system messages", which are heard by all devices. Any data not relevant to a receiving device is ignored.[35]:384 There are five types of message: Channel Voice, Channel Mode, System Common, System Real-Time, and System Exclusive.[85] Channel Voice messages transmit real-time performance data over a single channel. Examples include "note-on" messages which contain a MIDI note number that specifies the note's pitch, a velocity value that indicates how forcefully the note was played, and the channel number; "note-off" messages that end a note; program change messages that change a device's patch; and control changes that allow adjustment of an instrument's parameters. Channel Mode messages include the Omni/mono/poly mode on and off messages, as well as messages to reset all controllers to their default state or to send "note-off" messages for all notes. System messages do not include channel numbers, and are received by every device in the MIDI chain. MIDI time code is an example of a System Common message. System Real-Time messages provide for synchronization, and include MIDI clock and Active Sensing.[2]:18–35 System Exclusive messages System Exclusive (SysEx) messages are a major reason for the flexibility and longevity of the MIDI standard. They allow manufacturers to create proprietary messages which provide control over their equipment in a way that is more thorough than is provided for by standard MIDI messages.[5]:287 SysEx messages are addressed to a specific device in a system. Each manufacturer has a unique identifier that is included in its SysEx messages, which helps ensure that the messages will be heard only by the targeted device, and ignored by all others. Many instruments also include a SysEx ID setting, which allows two devices of the same model to be addressed independently while connected to the same system.[86] SysEx messages may include functionality beyond what the MIDI standard provides. They are targeted at a specific instrument, and are ignored by all other devices on the system. The MIDI Implementation Chart Devices typically do not respond to every type of message defined by the MIDI specification. The MIDI Implementation Chart was standardized by the MMA as a way for users to see what specific capabilities an instrument has, and how it responds to messages.[2]:231 A specific MIDI Implementation Chart is usually published for each MIDI device within the device documentation. Extensions Main article: MIDI usage and applications GM Standard Drum Map on the keyboard The GM Standard Drum Map, which specifies the percussion sound that a given note will trigger. MIDI's flexibility and widespread adoption have led to many refinements of the standard, and have enabled its application to purposes beyond those for which it was originally intended. General MIDI Main article: General MIDI MIDI allows selection of an instrument's sounds through program change messages, but there is no guarantee that any two instruments have the same sound at a given program location.[87] Program #0 may be a piano on one instrument, or a flute on another. The General MIDI (GM) standard was established in 1991, and provides a standardized sound bank that allows a Standard MIDI File created on one device to sound similar when played back on another. GM specifies a bank of 128 sounds arranged into 16 families of eight related instruments, and assigns a specific program number to each instrument. Percussion instruments are placed on channel 10, and a specific MIDI note value is mapped to each percussion sound. GM-compliant devices must offer 24-note polyphony.[88] Any given program change will select the same instrument sound on any GM-compatible instrument.[89] The GM standard eliminates variation in note mapping. Some manufacturers had disagreed over what note number should represent middle C, but GM specifies that note number 69 plays A440, which in turn fixes middle C as note number 60. GM-compatible devices are required to respond to velocity, aftertouch, and pitch bend, to be set to specified default values at startup, and to support certain controller numbers such as for sustain pedal, and Registered Parameter Numbers.[90] A simplified version of GM, called "GM Lite", is used in mobile phones and other devices with limited processing power.[87] GS, XG, and GM2 Main articles: General MIDI Level 2, Roland GS and Yamaha XG A general opinion quickly formed that the GM's 128-instrument sound set was not large enough. Roland's General Standard, or GS, system included additional sounds, drumkits and effects, provided a "bank select" command that could be used to access them, and used MIDI Non-Registered Parameter Numbers (NRPNs) to access its new features. Yamaha's Extended General MIDI, or XG, followed in 1994. XG similarly offered extra sounds, drumkits and effects, but used standard controllers instead of NRPNs for editing, and increased polyphony to 32 voices. Both standards feature backward compatibility with the GM specification, but are not compatible with each other.[91] Neither standard has been adopted beyond its creator, but both are commonly supported by music software titles. Member companies of Japan's AMEI developed the General MIDI Level 2 specification in 1999. GM2 maintains backward compatibility with GM, but increases polyphony to 32 voices, standardizes several controller numbers such as for sostenuto and soft pedal (una corda), RPNs and Universal System Exclusive Messages, and incorporates the MIDI Tuning Standard.[92] GM2 is the basis of the instrument selection mechanism in Scalable Polyphony MIDI (SP-MIDI), a MIDI variant for low power devices that allows the device's polyphony to scale according to its processing power.[87] MIDI Tuning Standard Main article: MIDI Tuning Standard Most MIDI synthesizers use equal temperament tuning. The MIDI Tuning Standard (MTS),ratified in 1992, allows alternate tunings.[93] MTS allows microtunings that can be loaded from a bank of up to 128 patches, and allows real-time adjustment of note pitches.[94] Manufacturers are not required to support the standard. Those who do are not required to implement all of its features.[93] MIDI Time Code Main article: MIDI timecode A sequencer can drive a MIDI system with its internal clock, but when a system contains multiple sequencers, they must synchronize to a common clock. MIDI Time Code (MTC), developed by Digidesign,[95] implements SysEx messages[96] that have been developed specifically for timing purposes, and is able to translate to and from the SMPTE time code standard.[5]:288 MIDI Clock is based on tempo, but SMPTE time code is based on frames per second, and is independent of tempo. MTC, like SMPTE code, includes position information, and can adjust itself if a timing pulse is lost.[97] MIDI interfaces such as Mark of the Unicorn's MIDI Timepiece can convert SMPTE code to MTC.[98] MIDI Machine Control Main article: MIDI Machine Control MIDI Machine Control (MMC) consists of a set of SysEx commands[99] that operate the transport controls of hardware recording devices. MMC allows a sequencer to send "Start", "Stop", and "Record" commands to a connected tape deck or hard disk recording system, and to fast-forward or rewind the device so that it starts playback at the same point as the sequencer. No synchronization data is involved, although the devices may synchronize through MTC.[100] MIDI Show Control A theatrical event operated by MIDI Show Control MIDI Show Control is used to cue and synchronize lighting and effects for theatrical events, such as the Waterworld attraction at Universal Studios Hollywood.[101] Main article: MIDI Show Control MIDI Show Control (MSC) is a set of SysEx commands which allows sequencing and remote cueing of show control devices such as lighting, music and sound playback, and motion control systems.[102] Applications include stage productions, museum exhibits, recording studio control systems, and amusement park attractions.[101] MIDI timestamping One solution to MIDI timing problems is to mark MIDI events with the times they are to be played, and store them in a buffer in the MIDI interface ahead of time. Sending data beforehand reduces the likelihood that a busy passage will send a large amount of information that will overwhelm the transmission link. Once stored in the interface, the information is no longer subject to timing issues associated with USB jitter and computer operating system interrupts, and can be transmitted with a high degree of accuracy.[103] MIDI timestamping only works when both the hardware and software support it. MOTU's MTS, eMagic's AMT, and Steinberg's Midex 8 were implementations that were incompatible with each other, and required users to own software and hardware manufactured by the same company in order to gain its benefits.[45] Timestamping is built into FireWire MIDI interfaces[104] and Mac OS X Core Audio. MIDI Sample Dump Standard An unforeseen capability of SysEx messages was their use for transporting audio samples between instruments. SysEx is poorly suited to this purpose, as MIDI words are limited to seven bits of information, so an 8-bit sample requires two bytes for transmission instead of one. This led to the development of the Sample Dump Standard (SDS), which established a protocol for sample transmission.[5]:287 The SDS was later augmented with a pair of commands that allow the transmission of information about sample loop points, without requiring that the entire sample be transmitted.[105] Downloadable Sounds The Downloadable Sounds (DLS) specification, ratified in 1997, allows mobile devices and computer sound cards to expand their wave tables with downloadable sound sets.[106] The DLS Level 2 Specification followed in 2006, and defined a standardized synthesizer architecture. The Mobile DLS standard calls for DLS banks to be combined with SP-MIDI, as self-contained Mobile XMF files.[107] Alternative hardware transports In addition to the original 31.25 kbit/s current-loop transported on 5-pin DIN, other connectors have been used for the same electrical data, and transmission of MIDI streams in different forms over USB, IEEE 1394 a.k.a. FireWire, and Ethernet is now common. Some samplers and hard drive recorders can also pass MIDI data between each other over SCSI. USB and FireWire Members of the USB-IF in 1999 developed a standard for MIDI over USB, the "Universal Serial Bus Device Class Definition for MIDI Devices"[108] MIDI over USB has become increasingly common as other interfaces that had been used for MIDI connections (serial, joystick, etc.) disappeared from personal computers. Microsoft Windows, Macintosh OSX, and Apple iOS operating systems include standard class drivers to support devices that use the "Universal Serial Bus Device Class Definition for MIDI Devices". Drivers are also available for Linux. Some manufacturers choose to implement a MIDI interface over USB that is designed to operate differently from the class specification, using custom drivers. Apple Computer developed the FireWire interface during the 1990s. It began to appear on digital video cameras toward the end of the decade, and on G3 Macintosh models in 1999.[109] It was created for use with multimedia applications.[104] Unlike USB, FireWire uses intelligent controllers that can manage their own transmission without attention from the main CPU.[110] As with standard MIDI devices, FireWire devices can communicate with each other with no computer present.[111] XLR connectors The Octave-Plateau Voyetra-8 synthesizer was an early MIDI implementation using XLR3 connectors in place of the 5-pin DIN. It was released in the pre-MIDI years and later retrofitted with a MIDI interface but keeping its XLR connector.[112] Serial parallel, and joystick port MIDI As computer-based studio setups became common, MIDI devices that could connect directly to a computer became available. These typically used the 8-pin mini-DIN connector that was used by Apple for serial and printer ports prior to the introduction of the Blue & White G3 models. MIDI interfaces intended for use as the centerpiece of a studio, such as the Mark of the Unicorn MIDI Time Piece, were made possible by a "fast" transmission mode that could take advantage of these serial ports' ability to operate at 20 times the standard MIDI speed.[2]:62–3[111] Mini-DIN ports were built into some late-1990s MIDI instruments, and enabled such devices to be connected directly to a computer.[113] Some devices connected via PCs' DB-25 parallel port, or through the joystick port found in many PC sound cards.[111] mLAN Main article: mLAN Yamaha introduced the mLAN protocol in 1999. It was conceived as a Local Area Network for musical instruments using FireWire as the transport, and was designed to carry multiple MIDI channels together with multichannel digital audio, data file transfers, and time code.[109][110] mLan was used in a number of Yamaha products, notably digital mixing consoles and the Motif synthesizer, and in third-party products such as the PreSonus FIREstation and the Korg Triton Studio.[114] No new mLan products have been released since 2007. Ethernet The computer network implementation of MIDI provides network routing capabilities, and provides the high-bandwidth channel that earlier alternatives to MIDI, such as ZIPI, were intended to bring. Proprietary implementations have existed since the 1980s, some of which use fiber optic cables for transmission.[2]:53–4 The Internet Engineering Task Force's RTP MIDI open specification is gaining industry support, as proprietary MIDI/IP protocols require expensive licensing fees, or provide no advantage, apart from speed, over the original MIDI protocol. Apple has supported this protocol from Mac OS X 10.4 onwards, and a Windows driver based on Apple's implementation exists for Windows XP and newer versions.[115] OSC Main article: Open Sound Control The Open Sound Control (OSC) protocol was developed at the Center for New Music and Audio Technologies (CNMAT) of the University of California, Berkeley, and is supported by software programs such as Reaktor, Max/MSP and Csound, and some newer hardware controllers, including the Lemur Input Device.[116] OSC can be transported over Ethernet connections at broadband speeds, but is poorly suited for use as a whole-studio solution, as to date it lacks widespread support from hardware and mainstream software. The increased size of OSC messages as compared to MIDI messages make OSC an impractical solution for many mobile devices, and its touted speed advantages over MIDI disappear when both are transmitted over equal media.[117] OSC is not proprietary, but is not maintained by a standards organization. Wireless MIDI Systems for wireless MIDI transmission have been available since the 1980s.[2]:44 Several commercially available transmitters allow wireless transmission of MIDI and OSC signals over Wi-Fi and Bluetooth.[118] iOS devices are able to function as MIDI control surfaces, using Wi-Fi and OSC.[119] An XBee radio can be used to build a wireless MIDI transceiver as a do-it-yourself project.[120] Android devices are able to function as full MIDI control surfaces using several different protocols over Wi-Fi and Bluetooth.[121] The future of MIDI A new version of MIDI tentatively called "HD Protocol" or "High-Definition Protocol" has been under discussion since 2005, when it was announced as "HD-MIDI".[27] This new standard offers full backward compatibility with MIDI 1.0 and is intended to support higher-speed transports, allow plug-and-play device discovery and enumeration, and provide greater data range and resolution. The numbers of channels and controllers are to be increased, new kinds of events are to be added, and messages are to be simplified. Entirely new kinds of events will be supported, such as a Note Update message and Direct Pitch in the Note message which are aimed at guitar controllers.[122][123] Proposed physical layer transports include Ethernet-based protocols such as RTP MIDI and Audio Video Bridging.[111] The HD Protocol and a User Datagram Protocol (UDP)-based transport are under review by MMA's High-Definition Protocol Working Group (HDWG), which includes representatives from all sizes and types of companies.[123] Prototype devices based on the draft standard were shown privately at Winter NAMM 2013 using wired and wireless connections.[122] It is currently not known if and when the new protocol will be picked up by the industry.[124] Because the cost of data storage in consumer products has dropped so much, MIDI music is more and more replaced by wave audio in computers, tablets and phones. MIDI connectivity and a software synthesizer is still included in Windows, OSX and iOS but not in Android. |
About us|Jobs|Help|Disclaimer|Advertising services|Contact us|Sign in|Website map|Search|
GMT+8, 2015-9-11 20:35 , Processed in 0.153661 second(s), 16 queries .
