What is the next step?

[Bach5G]

Rimsky
Hindemith
?

[paulyg]

David
Grondahl

[harrisonreed]

Troorkh

[Bach5G]

Troorkh

Sounds a little high (tessitura).

[Bach5G]

Troorkh

Sounds a little high (tessitura).

I’m not deaf:

(Wikipedia) When Lindberg received Troorkh, he considered it to be "practically unplayable", with 56 high Fs and 2 F-sharps. However, he was ready to premiere it in 1993, in which he received a standing ovation. Subsequently, Xenakis sent him 28 red roses, half a rose each high F, and stated that, in his opinion, Lindberg was the best trombone player at that time. This composition is his last composition for a solo instrument and orchestra.[2]

[Bach5G]

Sounds a little high (tessitura).

I’m not deaf:

(Wikipedia) When Lindberg received Troorkh, he considered it to be "practically unplayable", with 56 high Fs and 2 F-sharps. However, he was ready to premiere it in 1993, in which he received a standing ovation. Subsequently, Xenakis sent him 28 red roses, half a rose each high F, and stated that, in his opinion, Lindberg was the best trombone player at that time. This composition is his last composition for a solo instrument and orchestra.[2]

So, maybe a little out of sequenza (V) Harrison.

[harrisonreed]

At least you know about it now.

How about Kalevi Aho: Symphony Nr. 9?

[Mikebmiller]

Trombonology by Tommy Dorsey. Hardest thing I have ever tried to play.

[MJL]

What about the Arutiunian Concerto? Everyone knows his trumpet concerto, but the trombone concerto is good as well - playable though a few challenges, and tuneful.
MJL.