Welcome back to vinyl - we've been waiting for you.
French Horn -
Franz Danzi: Concerto for Waldhorn
Strauss: various Horn concertos
Teleman: Horn Concerto
standard horn joke: the difference between a French horn and a lawn mower is that you can tune a lawn mower. (heh :-)
String music -
Felix Mendelssohn: Overture 'The Herbrides' - Fingal's Cave
Vaughan Williams: The Lark Ascending
Rodrigo: Concierto de Aranjuez
Melancholy -
Rachmaninov: Isle of the Dead (pensive, forboding) and his Symphony No.2 - at least the start - find the Slatkin on Reference if you can.
Tchaikovsky: 6th Symphony, 'Pathetique' pretty much says it - Mehta's is good
Conan -
Brahms: Schicksalslied 'Song of Destiny' - I love big choral
Basil Poledouris: various Conan soundtracks on vinyl
And of course Wagner, already mentioned
For classical with nice sonics, here's a starter list
Wrt record cleaning, I use a Loricraft 3 and the Walker Prelude system augmented with Nerl Reagent Grade water.
Tim