microtuner

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An electronic device or audio software endowed with microtuning capabilities specifically designed and used to modify the tuning of musical instruments, hence allowing for microtonal scales, just intonation scales and tunings other than the twelve-tone equal temperament to be played (microtonal tuner).
• noun High-precision mechanical tuning device found on some vintage brass and reed instruments.