So my son plays the Euphonium and will need to pick and practice a classical music song for an audition to an arts high school next January, and we are looking to get some music books of appropriate level for him to play that is "Royal Conservatory of Music" ranked pieces (we are Canadian, unsure if RCM is more universally known or just for us Canucks) but my wife has been searching without luck online for some appropriate books for the euphonium.

Can anyone here recommend something suitable, or for a different instrument (such as the barintone b.c.) that we could get the book and have it translate across properly for him to practice for his audition? (It can't be pop music or band parts, must be the melody, and 3 minutes or so long).