Q: "How do I use MIDI "Expression" (Controller 11) in my sequencing?"

A: Expression, or MIDI Continuous Controller 11, is one of the original MIDI commands that define the actions of things like foot pedals, modulation wheels, and sliders in synthesizers. Most of the time expression used as a subset of Volume (MIDI CC 7), and you can use it to create natural crescendos and decrescendos in sustained-tone instruments, such as strings, wind, or synth pads. This way you can set an overall track level through volume and then adjust individual notes or groups of notes by applying increasing or decreasing the expression levels.

MIDI sequencers offer many ways to insert expression messages into your tracks: you can draw them in graphically, insert them in an event list, or use a menu-driven operation (such as Digital Performer's "Create Continuous Data" feature). Try this: create a sequencer file with just one track. Assign a violin, flute, or synth pad sound to the track and record a single note with duration of 8 beats. Now, using one of the methods mentioned above, insert a series of controller 11 (Expression) messages ranging from 0 to 127, that begins when the note starts and ends just before the note ends. Now play the track; you should hear a gradual increase in the volume of the note as the expression values increase. Of course, your sound source must be programmed to respond to expression changes for this to work.

Modern synths and samplers incorporate many more elements than volume into their expression parameters, to offer maximum sonic control. Try this with a Garritan Orchestral Strings' "EXP" instrument, which routes expression control to the modulation wheel: while playing an EXP voice, move the wheel to crossfade seamlessly between different string samples, each with a different velocity level. This emulates a surging crescendo or decrescendo that includes the changes in timbre that an actual string section would achieve.