allmusic 

Being positive about any album or song you hear. To never give bad reviews, or to only give them once in a while for obscure reasons. In reference to reviews usually given by allmusic.com.

That guy totally went allmusic on that new Simple Plan album, he gave it four stars!

allmusic by JFrosty December 23, 2010

allmusic 

Encyclopedia Musica. Vastly useful internet music database.

Yo, bitch, that new allmusic layout is some fucked up shit.

allmusic by Jim A. July 25, 2004

altmusic 

"Altmusic" or "Alt Music" is an abbreviation for the phrase "alternative music".

The abbreviation is commonly used when people are too lazy to actually spell out the whole phrase "alternative music" or hit a character limit. This abbreviation cost 9 less characters.

Altmusic may be shortened to 4 characters by typing "alt" followed by a music emoji but this isn't common since a vast majority of people that listen to alternative music are hipsters and think emojis are "too mainstream"

Courtney: Luke's instagram bio sais "altmusic" , what the hell does that mean?
Jessica: It means he listens to alternative music, duh.

altmusic by insta_lvke98 April 22, 2016