There are many duets in The Nine-Note Recorder Method for two sopranos or two altos. Beyond the Nine-note Recorder Method is mostly duets, for 2 recorders of the same voice.
Easy Duets and Trios for Soprano & Alto Recorders is a chance for soprano and alto players to make music together. This volume is also available for Tenor and Bass Recorders. Print this 70-page digital PDF after your $5 payment.
Click on pictures to see contents of books. Look under Christmas Music and Hymns for more collections of duets.