Thomas Cassell was raised in Southwest Virginia and now lives in Nashville, Tennessee. He has played alongside Billy Strings, the Bryan Sutton Band, Jim Lauderdale, Becky Buller, Missy Raines, and many more. He was a founding member of the progressive group Circus No. 9 before working on original music of his own. Cassell began with an instrumental album in 2018, Voyager. Soon after he released his first collection of original vocal material, What You Need to Prove.
In 2020, he was named the Momentum Instrumentalist of the Year by the International Bluegrass Association, and by 2021 he was named National Mandolin Champion. He went on to gain titles such as 2021 FreshGrass Mandolin Champion, and 2016 Rockygrass Mandolin Champion. He is a two-time alum of the Acoustic Music Seminar in Savannah, Georgia.