If you can’t play it on an acoustic guitar or a grand piano then it’s not a song.

Meaning of the quote

This quote by American musician Christopher Cross means that a true song should be able to be played on simple, unelectrified musical instruments like an acoustic guitar or a grand piano. If a musical piece requires a lot of complex electronic equipment to sound good, then it's probably not a true song. The core idea is that a real song can stand on its own without needing a lot of technology to make it work.