Tuning a piano is essentially the same as tuning your guitar, the difference being that on a guitar you've got six strings to perfect whereas your average piano has a good 230 strings, each string must be as perfect as possible. I tune my guitar almost every time I pick it up to play, whereas a piano tuning must last for a good 6 months. As a standard there are 88 notes but about 230 strings because the treble strings have 3 strings each to add richness of tone and volume, the thicker bass notes only having one or two strings per note.

A440 is a common term among musicians - it means middle A (ie. A4 on a standard keyboard) has been tuned to 440Hz (ie. air pressure waves pass a fixed point in space at a frequency of 440/second). This is standard concert pitch to which most instruments in the western world are tuned. Traditionally, European concert pitch is slightly sharper at A=444Hz, but to most people this small difference is difficult to notice at all. My father used to tune the Steinway concert grand piano in the Portsmouth Guildhall, where they had both English and European orchestras giving concerts on a regular basis, the English insisting on A440 and the Europeans on A444. The constant pitch-raising and pitch-lowering of the piano was potentially bad for the piano, and in the end my father had to put his foot down - from then on the piano was always kept at a compromise of A=442Hz to try and please both the British and the foreigners.

The average domestic piano, however, is not tuned before every concert, but twice a year. For this reason, when a piano hasn't been tuned for several years, it's probably gone flat and it is customary for the tuner to leave it slightly sharp, expecting the piano to settle back into concert pitch over the next few months or years. for example, if the piano was ¼ semitone below concert pitch, most piano tuners would try and leave it about 3-4 Hz sharp; if the piano was a tone flat then it might be raised to 6 Hz sharp.

Tuning a piano - essential steps

• Remove external panels.
• Compare a mid-treble note to the pitch of a standard tuning fork (commonly top C or middle A).
• Put adjacent notes in tune relative to the first note tuned. The most pure musical interval is the 8ve, followed by the 5th, the 4th then the major 3rd. So, for example, once you've tuned top C to a standard C tuning fork, you can use top C to tune middle C, then use middle C to tune the note one 5th above (middle G), then use middle G (G4) to tune G3, use G3 to tune D4, use D4 to tune D3, use D3 to tune A3, and so on. The next note would be E, which you can compare with C to see if the interval of a 3rd also sounds right - this is the way tuners check their progress. The sequence of 5ths is a cycle: C G D A E B F# C# G# D# A# F C returning to C. If all the 5th's were tuned perfectly, when you return to C you'd find you were very sharp. When the first keyboard instruments were developed, this didn't matter because people only played in 2 or 3 different keys and these instruments only had one or two 'black notes' per 8ve, music modulated to the dominant and perhaps sub-dominant and then back to the tonic and finished - no compromise had to be made in tuning perfection. But when music became more complex through the C17-C18th and the other black notes were added so that keyboards had the full chromatic scale as we have today, a compromise had to be made and 5th's were tuned ever so slightly flat (about ½Hz in the mid-treble) and major 3rds sharp so that the intervals sounded nice in every key. This modern system of tuning was actually a mathematical model developed over 2500 years ago by Pythagoras himself, but never had to be used until recently.
• When an interval is used to tune one note to another in the mid-treble, a 'pap's wedge' is used to stop the sound of two of the strings while the third string is tuned (remember in the mid-treble there are 3 strings to each note). After the first string of a note has been tuned, the other two are tuned to the first string to create a perfect unison.
• After the mid-treble section (known as the temperament) has been tuned, the rest of the piano can be tuned relative to the mid-treble using ascending and descending intervals of an 8ve.
• It's customary for a tuner to give the piano a quick checking over afterwards, to check 8ves especially round the bass-treble break-point, and to check that none of the unisons have moved.
• A good tuner will put the piano's external panels back on(!).