Sequencing is the process of programming a performance into a computer program to allow the computer to play the performance back to you. In this way a single individual can make music by programming the computer to play multiple performances simultaneously. Today this is typically done through a protocol called MIDI (Musical Instrument Digital Interface). MIDI is most commonly displayed in a Piano Roll format that shows when notes (Events) occur vertically, and time horizontally. Sometimes this information is also displayed in a list, but most musicians find the Piano Roll more comfortable, there are even some people that the “Piano Roll” display may replace traditional music notation. There are three basic ways to accomplish sequencing.

The first is to record a real-time performance from a MIDI controller. MIDI controllers are most commonly keyboards, but there are many new interfaces such as guitars and flutes. These controllers send performance data (not actual sound) to the computer or sound card, which the computer then records and stores against time. Essentially the computer is able to replicate the performance, giving the composer the ability to tweak and adjust the sound(s) associated with the performance. This is often the most efficient way to input a sequence.

The second way to accomplish sequencing is by manually placing notes on the timeline. Most software packages offer the ability to manually enter notes (and other performance data) directly on the time-line, this is usually using a “Pencil” tool. In this way a composer can write music that he/she may not have been able to perform otherwise. This procedure does not require a MIDI interface and is available to most composers out of the box with their recording application.

The final way of accomplishing sequencing is through a process often referred to “Step Input.” Step Input involves entering the performance using a MIDI controller, but not in real-time. The composer is able to enter notes one at a time and often use auxiliary buttons or keys on the controller to advance through the time line. As an example if the composer wanted to enter a C major triad, he/she could press the C key, then the E key then the G key, and then press the button to advance to the next time slot. Often other auxiliary buttons are also available to change note durations. This method takes some time to get used to, but down the road can be an efficient way to input a sequence.

MIDI offers much more data than just note placement and duration. MIDI data can be assigned to control virtually any parameter of a sound, but some of the most common are the Velocity, Sustain, and Pan. Velocity is a measurement of how hard a note is struck and can have a large effect on the timbre of the sound. Think about how different a guitar sting sounds when picked softly or very hard, there are differences in the sound other than just the volume, velocity tries to emulate these performance differences. All of this data is then fed to a sound generator.

The sound generator (typically a virtual instrument, sampler, or synthesizer) interprets this data and creates an audio signal. One of the advantages of capturing a performance via midi rather than acoustically is that you can apply that performance to any sound generator you would like to. In this way a keyboard performance can sound like drums, or guitar, or french horn.

The major drawback of MIDI is that it rarely can sound as authentic as a real acoustic performance. This is due to the fact that rich sample libraries cost a lot to produce, and can take an infinite amount of space depending on how accurate you would like to make them. MIDI also suffers from some latency and a limit to how much data can be transferred in “Real time.” MIDI data is transmitted serially (one 0 or 1 at a time), the transmit speed is only, 31.25 Kilobits per second (over a traditional MIDI 5 pin connection). This is fast enough for us not to hear the small amount of time that resides between the sounding of each note in a chord, but if several performances are being transmitted to several sound generators via the same MIDI connection some of these timing issues become recognizable to human perception.

That’s the basics, and the major advantage and disadvantage of MIDI and sequencing. For detail on how to implement MIDI in your home studio refer to your owners manuals for your gear.