If the purpose of your demo is to get your song picked up by a music publisher, A&R manager or a record producer, all they want to hear is the quality of the song—so don’t make the mistake of including a long instrumental section that doesn’t add anything to the song itself.
It’s okay to include a short instrumental hook or riff in the intro, or as a distinctive musical link between the end of the chorus and the start of the next verse. But a long, gratuitous guitar solo is not going to impress anyone and is unlikely to convince them to sign your song.
Obviously, if your aim is to secure a record deal for yourself or your band, an artist demo usually requires a little more instrumentation to showcase your sound, style and originality. But only include an instrumental break if you feel you need to demonstrate your musicianship or your potential as a live performer.
Keep it short though—ideally about four bars and no longer than eight. A two- minute solo or extended instrumental outro may simply test the listener’s patience!
# # # #