Many of GarageBand’s built-in sounds are samples—brief recordings of actual instruments. That’s why the grand piano sounds so realistic: because it is a grand piano (a $50,000 Yamaha, to be exact).
But behind the scenes, GarageBand’s sounds have been programmed to respond to various impulses beyond just pressing the keys. They can change their sounds depending on what other MIDI information GarageBand receives from your keyboard.
Sustain pedal. If you have a sustain or damper pedal, you can ride it with your foot just as you would on a piano. (It’s designed to hold a note or a chord even after your hands have released the keys.) Almost any MIDI keyboard—including the $100 M-Audio Keystation—has a jack on the back for a sustain pedal, which costs about $15 from online music stores like http://www.samash.com.
Key velocity. As noted earlier in this chapter, a number of GarageBand sounds respond to key velocity (that is, how hard you strike the keys). Most of the instrument sounds just play louder as you hit the keys harder, but some actually change in character. Acoustic guitars feature a little fingerboard slide; clavichords get more of a “wah” sound; Wah Horns also “wah” more; and many of the synthesizer keyboard sounds sound “rounder” as you hit the keys harder.
Using the correct technical language, you would say that these instruments are velocity-sensitive.
mod wheels. Pitch and Some keyboards, including that $100 M-Audio controller that ...