Josef Kueffner's 30 Duets for Two Trumpets is a collection of works at an intermediate to advanced level. They start at half page duets and progress to 1.5 page duets and their difficulty is progressive throughout as well.
The writing is very idiomatic, very tonal and brilliant, and they work particularly well in the studio setting with teacher and student, two students in performance, or for a trumpet hang of any possible description.
I have attached the first few duets for FREE in the samples so you can get a good look and give them a try, then you can grab an immediate PDF download above. Enjoy!