Also, in tune with.
In agreement in musical pitch or intonation, as in It's hard to keep a violin in tune during damp weather, or Dave is always in tune with the other instrumentalists. [Mid-1400s]
In concord or agreement, as in He was in tune with the times. [Late 1500s] The antonyms for both usages, dating from the same periods, are not in tune and out of tune, as in That trumpet's not in tune with the organ, or The lawyer was out of tune with his partners.
Examples from the Web for in tune
One of these may be called the in-tune system and the other the under-tune system.Cyclopedia of Telephony & Telegraphy Vol. 1