"In an accordion, the soul of the instrument is in the bellows. You can have a mechanical means of making the chord and not get a mechanical sound because the bellows is the part that is used to get the variations in sound that make it sound not mechanical."

When I find them, I love to collect those keybpards which use accordion reeds and have Stradella Bass buttons. They have an electric blower, so you can't get anythting but a constant drone, but they ARE fun, and purely mechanical.