Unisons are the most important skill one needs to be able to tune a piano.
Even an Electronic Tuning Device (ETD) can't help you to tune good unisons.
Unisons are two or more strings of the same note.
Each string produces its own partial series.
Each partial pair must be beatless.
For any out-of-tune unison, the higher up you go in coincident partials, the faster the partials beat.
So, you have to hear the higher partials and try to tune them beatless. Whatever speed you can get them to beat, the lower partials will be even slower
That's how we tune unisons by ear. We tune the higher partials beatless.
What's the hardest part of tuning pianos by ear? Hearing the partials.
So what if you can't hear the beating partials of an out-of-tune unison?
- You'll think it's pure,
- You'll have no idea it's out-of-tune.
- Other people with better ears will be able to tell that your unisons are no good but you'll have no idea.
So, how do you know if your unisons are good or not?
External Comparison: Compare the sound of the unison with that of a single string. There should be no difference.
Bandpass Filter Software: Use a bandpass filter like Ocenaudio and filter the higher partials to confirm if they are beating.
Real-time Bandpass Filter: Right now, the Piano Tuner's Ear is the only device that I know of that can do this. CLICK HERE to find out more about the Piano Tuner's Ear.
"If you can't hear the beating partials, you can't tune a piano."
