 While living New York, Grennan performed at the uptown nightclub Mikell's, where local musicians scored and adapted the beat for their own use.A reconstituted Flyers later emerged in New York as the rhythm that became known as disco.Grennan is also remembered for his work at Studio One (Coxsone Dodd), Treasure Isle (Duke Reid), Federal, and Beverly's (Leslie Kong) although he also recorded with Sonia Pottinger, Clive Chin, Byron Lee and Winston Riley, and nearly every other record producer of the era.