Tonic Sol-Fa is a British a cappella group that formed in 1996. The group is known for their unique sound, which blends elements of pop, folk, and world music. Tonic Sol-Fa has released seven studio albums, including their most recent album, "Twenty One," which was released in 2021. The group has toured extensively throughout the world and has performed at a number of prestigious venues, including the Royal Albert Hall and the Sydney Opera House.