early 14c., "a musical sound," unexplained variant of tone (n.). From late 14c. as "a well-rounded succession of musical notes, an air, melody." Meaning "state of being in proper pitch" is from mid-15c.
"bring into a state of proper pitch," c. 1500, from tune (n.). Non-musical meaning "to adjust an organ or receiver, put into a state proper for some purpose" is recorded from 1887. Verbal phrase tune in in reference to radio (later also TV) is recorded from 1913; figurative sense of "become aware" is recorded from 1926. Tune out "eliminate radio reception" is recorded from 1908; figurative sense of "disregard, stop heeding" is from 1928. Related: Tuned; tuning.