Bertalan> When you see p in the score, you play with less force on the
Bertalan> keys, with lower velocity. When you see ff in the score,
Bertalan> you play with much force on the keys, with high velocity.
That depends on the keyboard. On the organ I've sometimes played, how
hard you press the notes does asolutely nothing; to control volume you
use the swell pedal (and it works only on some stops). There's also
several milliseconds delay between playing a note and hearing it,
which is `interesting' to say the least.
I thnk the MIDI designers were mostly thinking about pianos when they
designed the protocols; CC11 for expression feels like an
afterthought.