How can one tell if a piano needs to be tuned? This is another post answering a series of questions about pianos given to me by students of Doug Hanvey.
I do have some real practical suggestions, but I’m afraid my primary answer won’t be very satisfactory:
It depends on you! Different people have different abilities to hear, notice, or be bothered by an out-of-tune piano. Depending on your experience, how you grew up, your native language, any other instruments you may have played and your innate sense of pitch, your ability to determine how out of tune your piano is will drastically vary!
To make things even more confusing, there are several ways a piano can be “out of tune,” which I elaborate on here.
Start at middle C and play every note moving up the keyboard. Listen for the notes to sound “clean,” “pure” and “steady” (these are words that I use, but it is surprisingly difficult to describe abstract sound with a common vocabulary). If notes sound “complicated” or “shimmery” or “twangy,” then your unisons (the three individual strings that make up one note) are out tune with each other. Also listen for continuity and uniformity of sound. If one or two notes sound very different or stick out from the ones around them, that’s also a pretty good sign your unisons are out and your piano should be tuned. Out of tune unisons are usually easiest thing to hear when checking a piano and the first thing to go out after a piano is tuned.
Testing octaves can also be helpful. I would start with the E’s on either side of middle C (E3 and E4 in the piano technician world). Then walk that octave down the keyboard chromatically and evaluate how clean, pure and consistent the octaves sound. If a piano has gone through a change in temperature or humidity the octaves in this section often go out of tune. This section seems most susceptible because of the transition from the bass strings on one bridge, to the regular treble strings on the other bridge. If the soundboard absorbs moisture out of the air, it expands raising the “bridges” at the bottom of the sounboard, but it usually changes one bridge slightly more than the other, making the bottom third of the piano out of tune with the rest of it.
Testing Pitch Level
You can also test your piano against a tuning fork or electronic tuner. Tuning forks usually are set to A440, which is the A above middle C. Strike the fork against your knee or something firm, then place the “handle” of the fork against the wood right under the keyboard. Touching the piano will help the tuning fork amplify its vibrations. Then play the A above middle C and listen for precisely the same pitch. If the unisons are out, you might notice its hard to compare the tuning fork with the note (because you may have 3 slightly different pitches coming from the piano!). If you have a high quality electronic tuning machine you can check it against A440. Most pianos go flat over time if not tuned, but they can go sharp as well if exposed to a humidity increase.
The Time Test
If it has been more than 6 months since your piano was tuned, it will certainly benefit from a tuning. If it has been more than a year since it was tuned, it probably really needs a tuning.