Fred Hersch’s short notes on the composition:

Song Without Words #4: Duet (2000) – It is a contrapuntal “duet” between the soprano and alto voices in the right hand.

Sheet is as recorded on:  Fred Hersch “Song Without Words” (Nonesuch 79612-2) – sheet written and edited by Fred Hersch.

Also available on fmscore as instrumental Bb-sheet as part of the Fred Hersch Jazz Compilation.