This looks like too much.
I think it’s OK. It follows the cover of the release, which is what users with the CD in hand would be looking for. If you would omit a couple of works, searching users might think that their release isn’t in the search results.
If you really want to shorten it, I guess you could call it “Rachmaninov: Daisies / Vocalise / Preludes; Schumann: Klavierstücke; Brahms: Four Ballades”.
PS The CSG calls for separating composers with a slash, but also separating works with a slash. But because here we have multiple composers and one composer with multiple works, I think separating composers with a semicolon looks much less confusing.
The possibilty for confusion also exists for the case where there are two composers for a work.
One work around used, I believe, is to separate the two composers with a comma instead of a slash.
Though this is indistnguishable for the naive from an unknown composer being credited by Surname, Firstname.
Who is/are the Composers for
Fmek, Cotue: Violin Concerto
Or even worse, ’
Fmek, Cotue, Dhawa: Piano Works
Your proposal would solve that problem too.
What is printed on the spine?
I would take that, usually.