The word "controller" is shorthand for the MIDI term continuous controller data, which is a type of MIDI information. Continuous controllers are used to add musical effects that change smoothly over time, such as volume changes (crescendos & decrescendos), amount of vibrato (which often increases in intensity over the duration of a note), and pitch bend to name a few. There are over a hundred types of controllers, although only about 30 are commonly used. In most cases, controllers affect whatever notes are playing at the time that they occur. In addition, they usually consist of a stream of individual data events that change their value over time. For example, a crescendo that occurs over the period of one bar might actually consist of 50 or 60 individual volume control MIDI events spaced only a few fractions of a second apart. In addition, each one has a value that is a little higher than the one before it (controllers have a value range from 0 to 127). To our ears, the net effect sounds like a smooth crescendo.
Since Controllers have this dual nature (individual events that constitute a smooth gesture) FreeStyle displays them in a way that lets you see where each event is, as well as the overall shape. Whenever you see a bracket in the controller view it indicates that there is a single event in effect for the entire duration of the bracket.
Note velocities (the “velocity” of a note determines how loud it is) are the one exception to the way that controllers are displayed. Since there is only one velocity setting for each note, they are drawn as vertical bars, rather than as a connected shape.
