Possible Clues:

• Key of Beethoven's Seventh
• Key with three sharps
• Three-sharp musical key
• Key of Beethoven's "Kreutzer Sonata"
• Key of Schubert's "Trout Quintet"
• Key of Schubert's 'Trout Quintet'
• Music key
• Key of Beethoven's Symphony No. 7
• Three-sharp key
• Key of Chopin's "Military Polonaise"