Possible Clues:

• Lacking traditional musical tone structure
• Of music, not written in any particular key
• Like much Schoenberg music
• In no particular musical key
• With great speed, a lock's opening without any key
• Hardly melodic
• Without a key that's found in coat on a line
• Like Schoenberg's music a great deal, Albert?
• Getting into flat on a ladder, without a key!
• Lacking pitch