Congress did not pass a law saying that mod wheels could be used only to add vibrato

A mod wheel can be a source of expressiveness beyond whatever default setting it might have. Granted, the periodic vibrato a mod wheel adds is something only a synth can do, but try adding vibrato with the pitch wheel instead—it will sound more human, and more like the vibrato guitarists use. Or, consider using a footpedal instead.

Okay! Now that you’ve freed up your mod wheel, here are some other uses for it.

• Tone control. With bass patches, program the mod wheel to roll off high frequencies, like an electric bass’s tone control. When you want the “bass” to lay back a little further, roll off the highs.
• Morph among patches. If you can assign multiple parameters to the mod wheel, that may allow for enough change to morph between completely different sounds.
• Add a suboctave. This is another fun trick for bass when you want to shake the floor.
• Increase drive/distortion. This is one of my favorite mod wheel applications. Sometimes adding a little “grit” can really increase a part’s intensity.
• Control the hard sync effect. Assign the mod wheel to the oscillator that when swept, produces the hard sync effect.
• Detuning. Sweep the fine tuning between oscillators for chorusing-like effects that you control.
• Vary decay time. This is handy for percussive parts, where you want a staccato effect for emphasis, and a longer decay for the release part of the tension/release equation.