This series of duets were written by Erik Veldkamp for brass players who are playing in their first year. Erik has always found it very helpful to practice duets, because you have to play in time (and in tune) and listen to each other.
Book three of his mixed duet series is made of duets with what I am calling Intermediate + level difficulty. This still includes a range that reaches up to G above the staff, but now it includes more chromatics and accidentals as well as more complicated rhythms overall. These duets are in a variety of styles, including jazz, making the stylistic element a new challenge as well.
What I love more than anything is a book that knows its place. These duets are for people who need to challenge their reading skills, work on blending and tuning, and practice ensemble playing. It is so easy to take a book like this and make it TOO HARD. It happens all the time. To make wonderfully creative duets that sound great and are fun to play while staying within a reasonable difficulty, now that is a challenge. And Erik has succeeded here like no other.
Samples are to the left and show the first and last duet so you get an idea of the difficulty progression. Have a listen to No.4 below, they are such nice duets!