I`m used to reading bass clef and tenor clef and even alto clef. If they were any clef changing it would be between bass and tenor clef. If trombone music was written in alto clef i would always think, it would just stay in alto clef for the entire work. It would not switch clefs. Recently though i came across a piece by Brahms which has the trombone part switching between alto and tenor clef. Has anyone ever read trombone music that consistently switched between alto and tenor clef? I personally find that really strange beacuse it weird switiching just bewteen alto and tenor clef.

which brahms, just curious because i have full parts and i just want to check.

Yeah, I see it every once in a while, although it is very rare. The whole reason why composers wrote in different clefs is because it used to define which horn to use. Bass clef for bass bone, tenor for tenor bone, and alto for alto bone. So yeah, it`s very rare to see alto clef parts change like that, but it does happen sometimes.

For a good workout on this, go out and get the Blazhevich Clef Studies book.