Re: Reed Tuning/wondering pitch

[Pat Missin <pat@xxxxxxxxxxxxx>]

Fernando wrote:
>
>I work on a project at my job for which I have the obligation of analyzing
>different reeds and their response to extreme low and extreme high flows.
>The lowest flow that makes that reed vibrate (an 8.2 mm long and 0.15 mm
>thick reed) is about 2 LPM (liters per minute), and a normal flow is about
>6-8 LPM.
>
>I always tune my reeds by drawing, not blowing, as it is done at the
>factories, where they use tuning tables.
>
>I use a device which eliminates the problem of condensation and mitigates to
>almost non-existance the problem of change in volume of resonance of my
>mouth. It is simply a box, about half a liter big, with a cushioned slot for
>the reed and a small tube coming out. This tube I use to draw air through
>the reed, with my own lungs. No big and noisy machines, and very
>inexpensive.
>
>The size of the box being quite big, any change in embouchure si relatively
>non-significant and doesn´t produce a change in pitch.
>
>I must warn you, though, that there are some very experienced customizers
>that don´t use tuning tables or devices, trusting their own embouchure
>technique and ear to achieve a better result.
>As my hearing is not as near developed and I have to retune my harps
>quickly, I use this method. I hope it helps others with problems like mine.

Well, if you have found something that works for you, I'm not going to
tell you that you should do something different. However, as one of
those people who doesn't use tuning tables and who claims to get
better results because of it, I thought I might list some reasons why
I don't like them.

First of all, a reed mounted on a tuning table (also known as a
provino, I believe) will usually play with a slightly different pitch
when it is connected to a human vocal tract. I don't fully understand
why, I just know that it does. I assume it something to do with
frequency pulling effects of differing resonant chambers and the like.
Also, you mention that you tune all of them by drawing air through the
reeds. The same reed played by drawing will tend to have a slightly
different pitch when played by blowing. Again, I'm not entirely sure
why, but I assume it is due to the effect of the reed chamber. (IIRC
Vern measured that draw reeds take a little more air pressure to sound
than similar blow reeds - that may be due to the same thing.) Then
there is the effect that the covers have on the tuning.

It is possible to compensate for these things by doing what they do in
harmonica and accordion factories. Set up a master plate, tuned and
adjusted so that it plays perfectly under normal conditions, then put
both the master plate and the plate to be tuned on your tuning table
and tune the latter so that it matches perfectly with the master. This
would be quite practical if you only played one or two different
harps. If all you ever play is a Hohner 270 in the key of C, then you
would set up your master and tune your spare reedplates to match that
one. However, sometimes you get slight variability even between
supposedly identical reedplates. Besides, if you are a blues harp
player, even if you only stick to one model of harp, you would need to
set up a master plate for each key that you play - that is a little
less practical. In my own case, I have diatonics in more than two
dozen different tunings (not counting my chromatics, or all my other
harps) and in a wide range of keys. Setting up a master for each one
would be even less practical and if you include all the different
harps I tune for my customers, I don't think it would be at all
feasible. 

Another big objection I have to tuning tables is that they tune the
reeds in isolation. This isn't a problem with chromatics, as the reeds
are isolated in normal use by having valves. However, pairs of reeds
that share a chamber in a standard diatonic interact. This interaction
needs to be taken into account when tuning and adjusting reeds. In
fact, I don't believe tuning tables have the flexibility to do
anything but the most rudimentary of reed adjustment. I can't imagine
setting up a harp for overblows without actually playing the reeds in
question.

Even with a nice variable air supply to the tuning table, it seems far
easier to test a reeds over a wide range or pressures by mouth rather
than a mechanical supply, allowing you to do those tests I mentioned
in an earlier email to get optimum tuning over a varying range of
playing pressures, as well as those little tests to check on the
health of a reed. (I know you use a mouth-blown tuning table, so these
comments only apply to those with a mechanical blower).

A tuning table does have the advantage of a nice steady "embouchure",
but sometimes that can be a disadvantage as well. When I tune a harp
in JI, I not only check octaves and adjacent intervals, I check a reed
against a lot of reeds to make sure that the harp is in tune as a
whole, rather than simply working on individual reeds one at a time.
For example, when doing the final tuning of a harp I will tune 4 blow,
then check it against 1 blow, 7 blow, 2 blow, 6 blow, 3 blow and 5
blow. This sounds time-consuming, but it only takes a few seconds with
the reedplates mounted on a comb. Full size tuning tables usually have
provision for sounding different reeds simultaneously, however each
pair of notes you select will be played with the same resonant chamber
under them. With a human player, this does not happen - adjacent notes
will inevitably be played with a slightly different mouth chamber to
notes an octave apart. Checking their tuning whilst playing "normally"
allows you to compensate for this, particularly if you know you have
(or your customer has) a tendency to flatten certain notes when
playing octaves, or whatever.

Don't get me wrong - I think tuning tables have their uses, but I
don't think you do as good a job with them as you can by tuning by
actually playing the harp. My golden rule for tuning, whether it's a
harmonica, a guitar, or whatever, is to tune the instrument under
conditions that are as close as possible to the conditions under which
it is going to be played.

>Fernando Bresslau, who cannot hear a difference of pitch smaller than 4 - 5
>cents.

Well, for a start, I am willing to bet that you actually can hear much
better than you think. Also, when tuning it's much more a case of
knowing what to listen for. Most people cannot hear differences of
less than 5 cents when notes are played one at a time. However,
differences of 5 cents in certain harmonic combinations are obvious to
most people. By listening to the beating between various intervals and
harmonics you can tune to a remarkable degree of accuracy with
comparatively little practice.

 -- Pat.