Possible Clues:

• Valved brass musical instrument
• Instrument old character used to accompany Jolson?
• What could play music in particular key, hard stuff
• Brass instrument an officer (Royal Navy) keeps in house
• A letter written about large brass instrument
• Instrument made by singer with husband in navy
• Instrument for a pound a point
• Instrument for a large prickle
• A large and mostly sharp musical instrument
• Instrument that's low even if fleet