Janelle Monae and Brother also set for London event
The festival is set to take place in Victoria Park on August 5, with Bombay Bicycle Club headlining.
Ticket-holders must be under the age of 18, but over 13 to attend. See Underagefestivals.com for more information.
The Underage Festival line-up so far is:
Bombay Bicycle Club
Dog is Dead
Frankie and the Heartstings
The Chapman Family
The Midnight Beast