- The Nuggets -- The Number Theory
- The Number Twelve Looks Like You -- The Nut and Bolt Band
- The Nutley Brass -- The NY Citizens
- The NYC Trio -- THE-O
- The O-Men & Their Luv -- The Oakville Children's Choir
- The O.A.O.T's -- The Objectives
- The Objectives -- The Obscure
- The Observatory -- The O'Byrnes
- The O.C. Rollers -- The Ocean
- The Ocean as Mistress -- the Odd CupL
- The Odd Drawn -- The Odessa Klezmer Band
- The Odessa Strange -- The Offero Project
- The Offhooks -- The Officialz
- The Officialz -- The Ogyatanaa Show Band
- The Oh Boy! Band -- The Ok Rivals
- The Okada Supersound -- The Old Adage
- The Old Bailey -- The Old Haunts
- The Old Home String Band -- The Old Romantic Killer Band
- The Old Salute -- The Olde Battleaxe
- The Oldest -- The Olivia Tremor Control
- The Olliephonic Horns -- The O>matics
- The Omega Baptist Church Choir -- The On Off's
- The On Up Downstairs -- The One I Hate
- The One Man Electrical Band -- The Oners