Rinaldo is an opera by George Frideric Handel, composed in 1711, and was the first Italian language opera written specifically for the London stage. Here is an arrangement for Cello and Piano accompaniment for the popular piece Lascia ch'io pianga (Almirena  act 2).  
With downloadable mp3 for audio help.  Six pages (4 page Cello and Piano and 2 pages Cello), 4:20' min.
Early Intermediate.

Deutschlandlied ("Song of Germany", also known as "Das Lied der Deutschen" or "The Song of the Germans"), was conducted by Joseph Haydn in 1797.
Here is a piano duet 4-hands arrangement, 5 pages (3 pages both hands, 1 page prima, 1 page seconda) with downloadable mp3 for audio help.

God Save The Queen, for piano duet 4 hands.
Pages: 4 pages (2 pages both hands, 1 page prima, 1 page seconda), with downloadable mp3s for audio help.

Les Plaintes de la Jeune Fille by F.Schubert for Flute and piano duet.
With downloadable mp3 for audio help.
Pages: 9 pages (7 pages flute and piano score, 2 pages flute solo) 2:19 min.