Possible Clues:

• Instrument shaped like a 69-Across
• Troubadour accompanier
• Old guitar-like instrument played by minstrels
• Instrument that's plucked
• Pear-shaped classical guitar
• Guitar kin
• It's featured in two Vivaldi concertos
• Clay covering used to protect old instrument
• Madrigalist's accompaniment
• Plucked instrument; a sealant