Bi-timbral describes a synthesizer or electronic instrument capable of producing two different timbres at the same time.

A bi-timbral synthesizer has two "parts" or "sound engines" that can operate independently. This allows you to play two distinct sounds simultaneously, either by splitting the keyboard or layering them.

• Example of Split: You can split the keyboard in half, playing a bass sound with your left hand and a piano sound with your right hand.

• Example of Layer: You can layer the sounds, making each key trigger a piano sound and a string sound at the same time to create a richer timbre.

It's a step above a monotimbral synthesizer (which only plays one sound at a time) and a step below a multi-timbral, which can play more than two sounds simultaneously (usually 8 or 16).