a succession of musical sounds forming an air or melody, with or without the harmony accompanying it.

a musical setting of a hymn, poem, psalm, etc., usually in four-part harmony.

the state of being in the proper pitch

to be in tune.

agreement in pitch; unison; harmony.

proper adjustment, as of radio instruments or circuits with respect to frequency.

harmonious relationship; accord; agreement.

Archaic . frame of mind; mood.

Obsolete . a tone or sound.

to adjust (a musical instrument) to a correct or given standard of pitch (often fol. by up ).

to adapt (the voice, song, etc.) to a particular tone, to the expression of a particular feeling, or the like.

to bring (someone or something) into harmony.

to adjust (a motor, mechanism, or the like) for proper functioning.

Radio and Television .

to adjust (a circuit, frequency, or the like) so as to bring it into resonance with another circuit, a given frequency, or the like.

to adjust (a receiving apparatus) so as to make it compatible in frequency with a transmitting apparatus whose signals are to be received.

to adjust (a receiving apparatus) so as to receive the signals of a particular transmitting station.

to put into or cause to be in a receptive condition, mood, etc.; bring into harmony or agreement.

Archaic .

to utter, sound, or express musically.

to play upon (a lyre).

to put a musical instrument in tune (often fol. by up ).

to give forth a musical sound.

to be in harmony or accord; become responsive. ?

tune in, to adjust a radio or television set so as to receive (signals, a particular station, etc.).

tune out,

to adjust a radio or television set so as to stop or avoid receiving (a station or channel).

Slang . to stop paying attention to a person, situation, etc.

tune up,

to cause a group of musical instruments to be brought to the same pitch.

to begin to sing.

to bring into proper operating order, as a motor

Before starting on our trip we should have the car tuned up.

call the tune

to decide matters of policy; control

He was technically running the business, but his father still called the tune.

change one's tune

to reverse one's views; change one's mind

She changed her tune about children when she married and had her own.

sing a different tune, to be forced to change one's ways, attitude, behavior

etc.

He will sing a different tune when he has to earn his own money.

to the tune of

Informal . in or about the amount of

In order to expand, they will need capital to the tune of six million dollars.