be in tune

1. To have the proper musical pitch. People don't realize how hard it is to be in tune when you can't hear yourself singing! Hey, man, I don't think your guitar's in tune. OK, stop—you guys aren't in tune, and the song doesn't sound right at all.

2. To be in agreement with someone or something. I'm sure she feels the same way I do because we're always in tune. Those two are best friends, so they're usually in tune about this kind of stuff. Unfortunately, the information we learned is not in tune with the doctor's claims.

be ˌin/ˌout of ˈtune (with somebody/something)

1 be on/not on the right musical note: They were both singing out of tune.
2 be in/not in agreement with somebody/something; be/not be happy or comfortable with somebody/something: He’s out of tune with modern ideas about education. ♢ I don’t like London — I just don’t feel in tune with city life.