45 RPM = vinyl record player = music. Bosom = a human chest as in, “he shall gather the lambs with his arm, and carry them in his bosom.”
So if you’re lying on your significant others chest, or as a child being held to your parent’s bosom, you’re probably feeling safe, loved, cared for, joyous, taken away from whatever else is going on in the world at that moment.
In that lyric, I feel as if the singer is saying he finds his peace, his joy, his contentment, his escape, his love in music. And everyone needs to find that thing for themselves. For many people it is movies or music.