Three preludes for piano duet 4 hands, by R.Hahn.
Includes :
The Little Red Lark, My Love's An Arbutus, The Willou Tree.
Contains separate sheet music parts for each player, and sheet music with both parts together.
With  downloadable mp3s for each player and both, and midi files for practice, 31 pages.

Three works for piano duet 4 hands. Adolf Terschak (1832-1901) Children's dance (Mazurka, Polka) Paul Hiller (Christmas Eve).
Includes downloadable mp3, 21 pages, intermediate.

The pleasure of love, is a classical French love song written in 1784 by Jean-Paul-Egide Martini (17411816).
Here is an arrangement for easy piano duet 4 hands.
With downloadable mp3 for audio-help, 2:28 min

Tagus an easy piano duet 4-hands composed around 1820 by Hector Berlioz (1803-1869).
Pages: 2 pages both hands, 1 page prima, 1 page seconda, 1:15 min, with downloadable mp3 for audio help.

Ten short Duets 4 hands themes from romantic and classcical era for early intermediate piano.
By Mozart, Beethoven, Chopin, Adam, Halevy, Donizetti, Weber.
Includes parts for both players.
With downloadable mp3's for audio help (21 pages).
First published 1877.