I've been to a few concerts (and recognize the same sound in recorded music) where the singer sings into a microphone and plays chords on a keyboard. The sound captured by the microphone isn't played back directly; it is modified according to the notes played on the keyboard. I've noticed the microphone is usually rather small (unlike traditional stage microphones). The resulting sound seems to be a blend between voice and synth. Usually you can distinguish the words being said if you listen. The effect is somewhat similar to a sonovox. What is this instrument called?