However, if you compose a song that requires a bend in pitch, you will need this feature. Most synthesizers have a jack in the back that allows you to plug in a sustain pedal. This is useful when using Keyboard Studies Software or if you are going to perform with the instrument. The polyphony of an instrument includes notes being held by the sustain pedal, and can range anywhere from 8-64 notes. This refers to the number of timbres that can be heard at the same time and becomes an important feature when composing or playing back songs.
Many instructional programs utilize multi-timbral playback in their lessons.
A keyboard controller is a MIDI keyboard without sounds. These devices trigger the sounds built into your computer. Most current computers have sounds built into them and by triggering those sounds with a keyboard controller, the sum result is that you have a keyboard synthesizer. The advantage of a keyboard controller is that they are less expensive than a synthesizer. The disadvantage is that the sounds built into most computers are inferior to that of most synthesizers.