Violin duos are familierr for violinists as they have experiences to play duos with their teachers. Duos have a long history since early baroque era to now.
We can classify duos by three categories for their purpose. Classification is not easy because most of the work have no clear description on how and why they were composed.
Duos for education. Major composers are Kaliwoda, Mazas and Pleyer.
Duos for domestic use. Haydn, Boccherini and other arranged works. I fell many of duos of Haydn, Boccherini are written for amateur players.
Duos for concert composers’ own performance. Duos of Aubert, Lecleir, Guignon, Viotti, Belwald, Berio and Wieniawski are difficult and may be written to show their technique for audience. Duos by Reger, Bartok and Prokofieff are serious.