One of my most frequently asked questions is: Do you tune by ear? Normally I reply, no, I use my fingers. Hah!
I do use what is called an ETD (Electronic Tuning Device) as tuning aid, but the ear is always the final judge. Tuning strictly by ear has become something of an anachronism. Yes, it can be done. Yes, it is flexing a bit to claim one does only tuning by ear. Yes, it makes it a whole lot more work, especially when a piano is grossly out of tune.
A new client had recently acquired this piano and asked me to come tune it. I arrived to find a fellow tuner’s initials and dates on a piano that was grossly below pitch. This tuner prides himself on strictly ear tuning, but I often find pianos he has tuned, like this one, grossly below pitch. Why is that? Because it is a lot more work to raise the pitch if you are strictly an ear tuner. Using the modern technology of an ETD takes out the intensive labor and allows me to focus on producing a tuning that is on pitch and rock solid stable. And polishing the result with my ear checking ensures it is sweetly in harmonious tune.