I highly recommend Norman Del Mar's authoritative three-volume study of
Strauss, published in the US by Cornell University Press.  He draws the
links to Mahler (especially the cow bells in the Alpensinfonie).  I've
always felt Strauss did himself no good by calling attention to himself as
a "musical realist." In every major work, there's at least one passage that
has nothing to do with realistic depction.  He's a Romantic, just as Mahler
was.

Steve Schwartz