non-music 

So-called music which is either someone talking (they call it rapping) about how they busted a cap in their wife's head over less than 7 seconds of unique sequences of tones (usually bass), or music where an electric guitar is strummed at 100% total harmonic distortion and someone screams worshipping praise to Satan but you can't understand them and it sounds like they are trying to throw up.

Most of what the radio plays these days is non-music. There is no melody.

non-music by Braveheart's thirst for blood November 8, 2005

Non-Mainstream Music 

Pretty much the opposite of Mainstream music. Rarely, if ever, gets on the radio or top 40, and it's not usually well known to the general public. Also known as "Underground Music".

Non-mainstream music includes bands/artists such as Dream Theater, Porcupine Tree, Dälek, etc.

Non-Mainstream Music by 1729 February 16, 2009