Sequencers

One of the most important devices in MIDI production is the MIDI sequencer. A sequencer is a digitally based device or a computer program that is used to record, edit, and output performance-related MIDI data in a sequential fashion. The recorded MIDI-related channel and system messages commonly represent real-time or non-real-time performance events such as note on/off, velocity, modulation, aftertouch, and continuous controller messages. After a performance has been “recorded” into a sequencer’s or a computer’s internal memory, the data can be edited and saved to hard or floppy disk. When the sequence is played back, the device outputs these MIDI messages to the various connected MIDI devices within the system to re-create the performance. Unlike a recorded performance in which the instrument’s sounds are produced under the direct control of a live player, a sequencer communicates real-time performance data to various electronic instruments, which in turn produce the performed sound.

Most sequencers have a design similarity to their distant cousin, the multitrack tape recorder, in that MIDI data can be recorded onto separate “tracks” that contain isolated, yet related, performance material that is synchronous in time. Each of these tracks can be assigned to any MIDI channel and may contain any number of performance-and control-related messages (within the memory constraints of the device). When played back, the instruments and devices in the system that are assigned to a specific MIDI channel (0-16) respond only to track (or tracks) transmitting on that particular channel.

The number of individual tracks offered varies widely from one manufacturer and model type to the next and ranges from 8 to over 500 tracks. Almost every system is capable of transmitting and receiving data over all 16 MIDI channels, although most professional sequencers can communicate data over two or more independent MIDI data lines, which enables them to address 32 or more separate MIDI channels.

  

Another important feature offered by most sequencers is the capability to edit MIDI data in the digital domain. Standard cut-and-paste editing techniques generally are offered, which enable segments of sequenced data to be cut, copied, or reinserted at any point in a track or to any other track. Complex algorithms for performing such tasks as velocity changes, modulation and pitch bend, transposition, and humanizing (the controlled randomization of performance data to approximate human timing errors that are generally present in a live performance), as well as control over program or continuous controller messages, can also be inserted and changed.

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MIDI Sequencers     Connecting a MIDI Keyboard to a Computer