"F#A#∞" is a musical composition by the American composer David Lang. It was created in 1997 and is known for its unique structure and emotional depth. The piece is written for a small ensemble and features a blend of vocal and instrumental elements, exploring themes of love, loss, and the passage of time. The title "F#A#∞" reflects the musical notes and symbols used in the composition. The piece has gained recognition for its innovative approach and has been performed by various ensembles worldwide, contributing to contemporary classical music's evolving landscape.