A character who attempts to play an unfamiliar musical instrument has a base 5% chance of producing a simple musical sound.  These odds are adjusted as follows:

  Add wisdom and intelligence, and subtract 25.

  For proficiency in music, add 15.

  For every proficiency in an instrument, add 10.

  Bards who have begun bardic studies add 10.

  The chance of success may not exceed 99%.  If the character does not play another musical instrument in the same musical instrument family (string, wind, horn, percussion), this is reduced to 80%.

  None of this applies if the instrument is a magic item covered by special rules regarding ability to play.