Possible Clues:

• Correctly pitched or adjusted
• Like musical instruments
• Adjusted the pitch of, as a piano
• Like good pianos and engines
• Prepared the pitch and square with a French top dressing
• Like a good-sounding piano
• Fixed a flat?
• Adjusted (musical) pitch
• The noted racing engine needs to be this to perfection
• 'And many a thing may hap ere -' (William Morris)