He has also released two full-length albums with action-adventure rock trio Ebu Gogo and two records with Orlando-based drum 'n bass hip-hop group One Drop.

Castleton is a founding member of Rhode Island band Gruvis Malt, with whom he has released five full-length albums as well as a number of various independently-released EPs.

In 2006, Castleton collaborated with playwright Cyrus Leddy to release the bizarre spoken-word album Grace Land[1] which chronicles the mundane life of Gary Tivoli, a clerk at a Staples store, including intimate details of his relationship with his girlfriend and his obsession with Seinfeld.

In late 2007 he released A Bullet, A Lever A Key, the progressive hip hop EP that tells the story of an ever-deteriorating life in reverse-chronological order, beginning with his suicide in 2054 and ending backstage at a "present day" performance.

His blog "The Great Consolidation" features entries from the future that expound on the storyline of A Bullet, A Lever, A Key and discuss his latest full-length album Home, the tale of a long term love affair interrupted by a zombie apocalypse.

In Fall of 2009 he toured with a trio featuring Eduardo Torres on drums and Gray Robertson on bass, playing 67 self-booked shows criss-crossing the US.

Gavin posted a video of the album artwork-making process on his YouTube channel featuring the work of Aaron Nagel, Brendan Bell, Justin Muir, and Lorna Carman.

In the Fall of 2010 the Castleton Trio toured to the east coast with Lex Land and Happy Body Slow Brain, who both joined him on stage throughout the show.

On June 2, 2017, they released the FutureCastle EP on limited edition vinyl, featuring four cover songs (including Castleton's arrangements of Chicago's "If You Leave Me Now" and Hall and Oates' "Maneater").

On October 31, 2018, Castleton posted a lyric video for his Halloween single "I Choose You," inspired by the Teddy Perkins episode of Donald Glover's show Atlanta.

On June 12, 2021, Castleton has left The Dear Hunter, citing being at a point in his life that he cannot "[contribute] the appropriate time, energy, and focus" that the "many amazing and ambitious TDH events and releases" would require.