phly23:Hey, here's a great exercise that I Started doing to develop my "Drawbar ears"
Simply call up any"Black key" preset, and then try to replicate each one as best as possible using the drawbars on either manual.... try to distinguish each individual drawbars
pitch, color and essence...Quickly switch back and forth until you get
it each bar at a time .I work it until I cant tell the difference
between the preset and my manual setting! This has helped me immensely in being able to quickly emulate different sounds I hear created on a Hammond~
And then start on the white ones? 
Geoelectro
Organ - Yamaha FX-1 - (2) TM-1 speakers.
Synths - Korg Triton, Yamaha P-80
Softsynths - Native Instruments Kore 2, Komplete 5, Omnisphere, VB-3.