ShiroKuro I think $20 seems appropriate in this case, more as a token of appreciation than tipping.
My tech always tells me that there is no need of tipping for his tuning service. So I find other ways to thank him such as wines and opera tickets. We are like friends now 😄
Here is what I found from googling—
The Tipping Dilemma: To Tip or Not to Tip
When it comes to tipping your piano tuner, the general consensus is no, it is not customary. Unlike some service industries where tipping is a standard practice, piano tuning operates on a different etiquette. Piano tuners typically charge a fee for their services, reflecting the expertise and time invested in ensuring your piano sounds its best.
Why Tipping Your Piano Tuner Isn’t Customary:
Piano tuning is a professional service that is compensated through a predetermined fee. Unlike waitstaff or delivery drivers who rely on tips as a significant part of their income, piano tuners set their rates to encompass the full value of their service. Tipping is not expected, and most piano tuners do not factor it into their pricing structure.