The only thing copyrightable is the melody and the lyrics (for the most part) there are a few exceptions but generally speaking, you can not copyright chord progressions, the groove or feel of the song, the rhythm, short common language phrases or titles to the song.
Everybody uses the 1/4/5 blues/rock prog, and how many hit songs have been named "Heartbreaker"?
What constitutes a non-copyrightable short phrase vs one that is copyrightable? That, my friend, is up to a jury of your peers, should it come to that. Same thing with a melody.... obviously some note patterns will be repeated from one song to the next....
Men At Work lost a lawsuit on 5 notes. A jury thought it was a rip of the kookaburra song in the melody of the song Men At Work Land down under.
Sir Paul lost on 3 notes .... My Sweet Lord
Yet, Lady A has not been sued for Need You Now as a rip on Eye In the Sky by Alan Parsons.
Go figure.