To tune meantone, you need to first know how to tune unisons and octaves pure. If you have not yet figured
this out, make a half-hour appointment with someone who has. Your local harpsichordist will do, or your local piano or organ
tuner.
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You start with a pure beatless third: tune middle c, called c', and then tune the e above it, e', making
a pure third to it. In equal temperament one is used to 6 or 7 beats in that third, making it 'rich'-sounding to the modern
ear. But here we are looking for purity, so we make it smaller than an equal-tempered third until the interval (the two notes
played together) is beatless.
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Tune 2 pure octaves, one from middle C up and one down, and the octave from e' down (and check to make
sure c-e in the lower octave is also beatless).
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Tune the fourths and fifths c'-g, g-d', d'-a, and a-e' (already tuned, and leave it!) so that they average
out (this, in a sense, is the 'mean') as close to pure as thay can be and still arrive at the pure third e'. This means about
2 beats per second in each fifth or fourth.
n. b. there are other 'meantone' tunings, 1/3 comma, 1/6 comma, even 1/12 comma which is what we know as
equal temperament; but they produce few pure intervals; getting everything equally out-of-tune is what you have to do for
them, whereas in classic quarter-comma meantone the drill is to get some things exactly in-tune. This is not a hard thing
to tune, this is an EASY thing to tune. Equal temperament is hard.
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tune pure octaves to each of these notes, g up to g', d' down to d, a up to a'.
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From now on you merely tune pure thirds:
g-b (then tune a pure octave up to b', check with g', already tuned)
a-f (tune a pure octave up to f', check with a')
d'-f#' (tune a pure octave down to f#, check with d)
a-c#' (tune a pure octave down to c#)
d'-b flat (tune a pure octave up to b'flat')
g to e flat (tune a pure octave up to e-flat', check with g')
e to g# (tune a pure octave up to g#', check with e')
[sometimes one tunes c down to a flat instead of e up to g#, if one has the choice and it fits the music
one is working on better; or one can put in a d# rather than an e flat. One can customize this tuning any number of ways,
actually, for instance by picking a different starting point]
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Now you check to make sure major chords in your middle two octaves on F, G, A, B flat, C, D, E flat and
E all sound good, and that major chords on F sharp, D flat and A flat sound awful. Tune pure octaves down to the bottom and
up to the top of the instrument. And you are done.