A servo is an angular motor... From what you've said you don't need to set-to a particular angle. For example, you could use a servo to set the volume or tone knob on an electric guitar (although that's not the best way to adjust/set volume/tone digitally.) Servos are also geared-down so it might be a little slow for a beater/striker.
You probably want a DC motor or a solenoid. The difference/downside is that DC motors & solenoids don't have a built-in driver circuit.
Or... I can imagine a piano-like instrument with the keys arranged in an arc. A servo could be used to rotate a solenoid over the desired key before striking... But that's not what you want.