Possible Clues:

• Key of Beethoven's Piano Sonata No. 12
• If one's not sharp, by the sound of it, one may still get this apartment
• B sharp equivalent
• 'Perhaps a part meant to sound close to 6 down (1,4)'
• Most common key of Chopin's piano pieces
• G-sharp, alternatively
• Black piano key above G
• Major key of Chopin’s “Heroic” Polonaise
• It’s a semitone above G
• Key just above G