An instrument that starts with the letter A?

yes there is such as:

• Alto Horn
• Alto Saxophone
• Alphorn
• Accordion
• Acciaccatura
• Acoustic Guitar
• Aeolian Harp
• Aeoline
• Aeolodicon
• Aeolo Melodicon
• Aeolopantalon
• Aerophone *
• Aulos
• Arghul
• Albisiphone
• American Organ
• Amorschall
• Anemocorde
• Angklung
• Angle Harp
• Antara
• Anvil
• Apollonicon
• Appalachian Dulcimer
• Arara
• Arched Harp
• Arghul
• Armonica
• Armonica A Bocca
• Arpa
• Arpeggione
• Arpicordo
• Arabal
• Atabaque
• Autoharp
• Automatophone