Aural vs electronic tuning - which is better?

One of the questions I sometimes get asked on my rounds is about electronic tuning devices (ETDs) for piano tuning - do I use one and are they any good?

The picture above is of a Korg OT-120 chromatic tuner, which I'm "testing" with a tuning fork. In my opinion it's one of the best chromatic tuners out there. I use it to set the first string when tuning a piano, to check the piano is on pitch (although I can tune to a fork, it takes a little longer). This is the only piece of electronic equipment I have.

After this, the electronic tuner has done its job and gets put away - it can't be used to tune a whole piano - and I complete the entire remainder of the tuning by ear. This isn't because of any fault with the tuner itself - rather it's because of the way piano strings behave.

When a string vibrates between two fixed points, it vibrates separately through portions of its length (whole, half, one third, one quarter, one fifth and so on), which create additional tones (called overtones or partials) in addition to the fundamental frequency. Thus, A below middle C, which should have a frequency of 220Hz at standard pitch, will also produce overtones at 440Hz, 660Hz, 880Hz and so on.

However, because a piano string is slightly stiff and not perfectly flexible, the overtones actually end up being slightly higher in pitch than they theoretically should be. When a piano tuner is putting the instrument into tune, (s)he is actually matching the overtones of lower notes to the fundamental pitch of higher notes. This leads to the phenomenon of "stretch" - the octaves on a well-tuned piano are actually wider than they theoretically should be. The reason for doing things this way is simply that the piano sounds better. When tuning aurally, the ear listens for these consonances and stretches the tuning automatically (after proper training).

This brings us back to the question of the tuning devices. The Korg is a chromatic tuner which gives us theoretically correct frequencies, so if we used it to tune a whole piano, the "stretch" would be missing. Most people agree that a piano tuned this way sounds pretty awful!

However, there are some modern software applications that are able to sample the sound of the piano and calculate a suitable stretch. Most of these applications cost from a couple of hundred pounds upwards. This is the point where the controversy starts.

Which is the better method?

Some people claim that the aural method gives a better tuning because the electronics can never replicate the human ear. Others actually claim that "electronic/ computer accuracy" is better than aural tuning; which is correct?

The first thing to understand is that the ETD is a tool for tuners, not a tool that makes someone a tuner. There are other important parts of tuning technique, for example tuning unisons (most notes have three strings) and almost everyone agrees that the only way to get really good unisons is by ear. This is a tough enough job in itself.

Although I don't use one myself, I believe that ETDs have sometimes acquired a much worse reputation than they deserve, due to the misconception that they will allow someone with no skill and experience to tune a piano. In the hands of capable technicians, some of whom do use these devices, excellent tunings can be produced. However, in these cases, the technician is using experience and skill, listening to the tuning in conjunction with the ETD, to get a good result. Some tuners find they are able to achieve good results more quickly in some circumstances with this method.

Simply trying to tune by looking at a needle without listening to notes and intervals does NOT give good results. Any skilled tuner should be able to listen to and appraise the work they have done, to check what the electronic device is telling them is correct. Tuning a piano is about making it sound good, not about pegging it to a set of mathematically "correct" frequencies.

My reason for not using an ETD is a personal one - when I'm tuning, I just find it a distraction. This is a comment on me, not on the quality of the equipment.

Conclusion: some skilled tuners use purely aural methods and some use electronic tuning devices. Either method is fine, but the tuner must have the skill and experience to be able to listen to the work they have done and check whether it's a good tuning or not.