One of the things that makes a vibraphone special is it’s ability to, well, vibrate. Or better yet, create a sort of vibrato with the built in mechanism of a motor. A vibraphone’s motor allows a player to control fans built into the resonators which turn at various speeds to create different intensities of vibrato. While different models of vibraphones will have different mechanisms on their motors, a constant is that they will all have different speed settings, allowing a shift from no motor, to barely any, up to very fast.
Keep in mind, one needs a free hand to manipulate the motor! You can’t quickly pulse block chords while simultaneously changing motor speeds.
The status of the motor is typically notated simply as “motor off” or “motor on”, perhaps with the attribute of slow or fast added to it. However, it could be desired to notate a change in the status of the motor, which could be displayed like so:
It could also be ideal to create some sort of abbreviations to avoid getting too wordy in your score.
Lastly, it’s safe to assume that vibraphone motors will create some noise. This isn’t always the case, but it’s good to be mindful of the motor’s status in extremely quiet sections of a piece.