MIDI Basics Think of MIDI as an easily connected network between multiple devices. (They dont´t even need to be computers or instruments!) In MIDI there are thousands of electronic messages, but three: Note On, System Exclusive, Program Change are used by 99 % of all MIDI applications. The most basic MIDI function, Note On, tells the instruments what notes to play. In this regard, MIDI is similar to an electronic form of an old-style player piano, where a hole punched in a sheet of paper forced a key down on the piano´s keyboard. MIDI performs this task electronically. The designers of MIDI had a good bit of forethought and made the standard extensible through the use of System Exclusive commands. These commands are sent with an introductory special code that is ignored by all but the desired receiver. Since synthesizers have the ability to alter the sounds of their musical output, a command called Program Change instructs them to change their program. MIDI is a acronym for Musical Instrument Digital Interface, a standard method for electronic musical equipment to pass messages to each other. These messages can be as simple as 'play middle C until I tell you to stop' or more complex like 'adjust the VCA bias on oscillator 6 to match oscillator 1'. MIDI was developed in the early 1980s and proceeded to completely change the musical instrument market and the course of music. Its growth exceeded the wildest dreams of its inventors, and today, MIDI is entrenched to the point that you cannot buy a professional electric instrument without MIDI capabilities. Unless you are a musician, you might have ignored this startling growth. But today, with multimedia computer as it driving force, the MIDI revolution is on the verge of taking over the mainstream personal computing market. Roland was the first company to produce a MIDI processing unit, the MPU-401. This made possible the productive relationship between computers, electronic musical instruments, and musicians. Although some keyboards have hardware sequencers built in, software sequencers combined with a MIDI interface greatly expand the flexibility and memory capacities of MIDI sequencing. MIDI specifies 16 separate MIDI Channels. Therefore, with one MIDI cable you can control up to 16 different instruments at once. The concept of MIDI Channels is similar to the idea of television channels. Each television station sends a signal within a particular frequency range. Your television set receives many different ranges (or channels) at once. You then tune your television set to a particular frequency range. You may change ranges (channels) and the program displayed on your picture tube changes accordingly. To relate this to MIDI, imagine you have a keyboard that sends out on MIDI Channel 7. You record a part into your sequencer. As you play back the sequence, you decide that you want to have the MIDI information control a synthesizer set to a trumpet sound. You would then set the synthesizer to receive on Channel 7, and the MIDI data from the sequencer would cause the synthesizer to play. Another method available on many sequencers is to change the Channel assignment on the recorded part to match the synthesizer's MIDI receive Channel. Regardless of which device does the Channel tuning or changing, the point to remember is that both the sending device (e.g., the sequencer) and the receiving device (e.g. the synthesizer) must be set to the same MIDI Channel, or no sound will result. Drums are usually set on Channel 16 for base level and Channel 10 for extended level. Many different percussion sounds are on one Program Change Number (usually Number 0). To choose a particular percussion sound use the [Percussion Key Map] to see which notes represent which percussion sounds, then enter those notes in the Drum Track in MIDI List View or Score View. This is somewhat confusing, because the notes in the drum track look like they indicate the pitch of a percussion sound, but they do not. They only indicate the type of percussion sound, such as Bass Drum, Splash Cymbal, or Maracas. Entering a middle C (C4) note in the drum track plays a Hi Bongo, while entering an F above middle C (F4) plays a Low Conga, not a higher pitched Hi Bongo. Unlike other tracks in the score the location of the note on the Drum Track does not correlate to higher or lower pitched instrument sounds. It is only a way of defining which percussion sound you want. There are two MIDI message types: Channel messages and System messages. A Channel message includes a Channel number within the message. It is received and understood by any device which is set to that particular Channel, and ignored by any device set to a different Channel. The most basic Channel message is a Note On message. When you press a key on a synthesizer keyboard, a Note On message is sent out with the specific key number encoded within it. When you release the key, a corresponding Note Off message is sent. Other information can be carried by a Channel message, such as Velocity, Volume, Pitch Bend, and Aftertouch. A System message is meant to be received and understood by all devices that are connected, regardless of their Channel setting. These messages control synchronization between devices, as well as special manufacturer-specific modes of operation. A Program Change message causes any devices tuned to the same Channel to change internal settings corresponding to the number sent. On many synthesizers, this causes a change in patch (or instrument sound). MIDI specifies a possible range of 128 Program Change numbers. Most manufacturers have organized patches in different sequences; for example, Program Change 45 may call up a trumpet on one synthesizer and a harpsichord on another. As of this writing, there is a new standard for Program Change assignments between different synthesizers called [General MIDI], but instruments following this standard are just beginning to appear. Tracks are not really part of MIDI, but most sequencers use the concept of tracks on which MIDI data is recorded. We mention it here to distinguish tracks from MIDI Channels. In a professional recording studio, a multi-track tape recorder is one that records on multiple sections of the tape. Each section is a discrete area called a track. Even though you can record an entire orchestra on one track, you gain much more flexibility by recording each instrument on its own track. This way, if you find that an instrument was too soft or loud, you can adjust that instrument without affecting any others. The same holds true for MIDI sequencers. You can record each instrument on its own track, and later go back and adjust or edit only the MIDI data on that particular track. It is easy to get confused when you look at the number of MIDI Channels (16) compared with the number of sequencer tracks (often many more). Why have more than 16 tracks? A look at traditional music recording can help to answer this question. In most multi-track studios, even if you are recording a small group (with 4 instruments), you will use many tracks for partial or alternate takes. Possibly you will put the guitar playing verse 1 and chorus 1 on track five, and then put the guitar playing the second verse and chorus on track six. Or you may record ten versions of the sax solo, and choose between them, or put together a final solo that incorporates pieces from many of the takes. With only 4 tracks to record the above 4 instruments, you lose the ability to experiment. In a MIDI sequencer, you can make a copy of a track before going off the deep end with editing features, knowing there is an untouched version to revert to if you decide that you have gone too far. A common technique is to place Program Change messages, MIDI Volume messages, various Controller messages, or Pitch Bend messages on individual tracks. This way, you can mute or disable the effect of these messages selectively. Imagine that you have a Synth Module (a
synth with only sounds, there´s no keyboard), A synthesizer with
keyboard and a Computer with a MIDI interface. There are basically three MIDI cables: MIDI IN,
MIDI OUT and MIDI THRU.
A MIDI computer doesn´t have to cost a fortune, but it is
better to have a fast machine these days if your wallet allows you to. To record a song you need something that can give input to
the sequencer. To play and record music you´ll need a [Sequencing Program],
such as Cubase, Cakewalk or Voyetra DOP. |
The MIDI OUT on the computer is
connected to the keyboard´s MIDI IN.