[Adamus]

most part a ear(brain)muscle coördination. And loads of practising of course -esp.tuning unisons. my experience is it's boring most of the time when tuning 20plus (mostly old) pianos a week.

 

[Adamus]

I have a yamaha tuner from 1980, the first small one (?)

 

[Adamus]

try smartphone (ios/android) apps. www: pianotechniciansguild, Reblitz book about repairing etc.

smart move? the internet has a truckload of info......