I want to attend the machine head concert at this place but it does not specify the age necessary to enter the place because my friend is not 21 years old

It's right on the event page of Webster Hall's site... 16+ However under 21 can't drink alcohol

I think age check is to identify the people that are drinking age that is all

18 to go in to the last show we attended. Dunno if that's all shows or just because Heilung has a topless character...

Some events are 19 others are 22