From Custom Solutions of Maryland:
Music Assistant is a utility to help you set a tempo and tune your instruments. The metronome mode has a range of 40 to 210 beats per minute. The tune-up mode provides three choices: hear 440 Hz (the A above middle C on a piano), hear any note on a full size piano, hear notes to tune instruments. In addition, the user can tune using LucyTuning and Offset by Cents methods. The utility includes default information to tune instruments and you can add, delete and change this information (Instrument Data window accessible from the menu bar) which is saved between sessions.
What's new in this version:
Version 2.3.0 is compatible with Yosemite's default security.