I can't play piano or read music, unless "Every Good Boy* Does Fine" counts... I do know some music theory, and can play chords.
I have a $199 midi keyboard and a couple of inexpensive sound modules. I either am plugged in direct for recording, or plugged into a PA when I need to make loud noises. I use it for creating bass lines, and backup parts - piano, organ, synth, sax, etc., for my homebrew studio.
* Sorry for using the word "boy" in this post...