Related Clues:

• What's instrumental in services that may be provided by donor
• One's musical ear, say?
• It has keys and stops
• Hymn instrument
• Bach provided notes for this publication
• Big wind instrument
• Bach played it
• Keyboard kin
• Mozart's "King of Instruments"
• It's instrumental in arresting minor gangsters
• An ear, perhaps, for music played on this
• Eg, the liver
• Instrument decapitated Welshman
• Major ganglia - part of the brain, perhaps
• An instrument for gangsters to conceal