Possible Clues:

• Is to make better about having to ad-lib
• Not follow the book
• Is impressed by better jam
• Ad-lib one's better without
• Play off the cuff
• VIP is more prepared to make do
• Vamp needs to make up
• What a player who thinks on his feet will do
• To get better, one's called in to play by ear
• One member is dealt with over ad lib