EarTest is an ear training program.  It is loosely based on the method
described in the David L. Burge Perfect Pitch ear training course that you
may have seen advertised in music magazines. EarTest plays a note, you
must respond by playing the same note on a MIDI keyboard.  It has several
levels, from very easy to incredibly difficult.  If you don't believe in
learning perfect pitch, you can use it to hone your relative pitch (you
begin be learning the notes of the C major scale, so you can just think of
do-re-mi and forget the perfect pitch stuff if you like).  Requires MIDI
card & keyboard. (DOS freeware)