Bass player with the popular wizarding band The Weird Sisters, and a big Kenmare Kestrels supporter (FW). According to the Daily Prophet, he was married in the fall of 1995 (OP14). He attended Dumbledore’s funeral (HBP30).
Playing the Bass Guitar (which we can assume is not electric but magical)
Other canon notes and references
Tremlett was Wizard of the Month on JKR's website for July, 2004 (JKR).