Trained By: Bard
If you have a musical instrument in your bag, such as a flute or harp, then all you need to do is double-click the instrument. A skillcheck will determine if you just make random noise with the instrument or if you are able to actually make music.
This skill is required for Bard because their magic is in their music. Both peacemaking and provocation skills for Bards require musicianship skillchecks.
For Provocation to work, you must have an instrument in your backpack.