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.

Five piano duets 4 hands. Reinecke Carl (1824-1910) Cradle song and Tarantella, Splinder Fritz (1817-1905) Immortelles 1,4,7.
Includes downloadable mp3. Intermediate, 24 pages. E-mail: musicBooknet@gmail.com

Piano duet is Fun a bright cheerful, rythmical and fun duet for piano duet (1 piano 4-hands).
By Juan Morel Campos (1857-1896).
Transcribed for early-intermediate to intermediate level.
Includes downloadable mp3 with both parts and separate parts with count-in measures for play-along learning purposes, 2:20' min, 13 pages (primo 3 pages, secondo 3 pages, both 6 pages, cover 1 page).

A little characteristic piece for piano solo, by Carl Philipp Emanuel Bach (1714-1788), 2 pages, 61 bars, 1:41 min, intermediate level, with downloadable mp3 for audio help.