[Harp-L] Fwd: Imaginary Hole Technique

["Rick Epping" <rickepping@xxxxxxxxx>]

Joel asked if I'd forward to harp-l the message below.

While the fundamental frequency of the missing high note is found in the
first overtone, or second partial of the note an octave lower, the series of
overtones that would be found in the note produced by the missing reed,
which gives the note its characteristic timbre, are not.  In the audio file
I sent Joel I played a rapid passage of octaves, in the midst of which a
single note, an octave lower, was played where the missing reed would occur.
The reasons why it may seem as if the missing note is there are, I would
speculate, threefold:
1. The ear expects to hear the high octave note, based on the previous
passage of octaves.
2. The first overtone of the lower octave note provides an approximate,
albeit incomplete, substitute for the missing note.
3. The notes in the audio sample are of short enough duration that the ear
doesn't have enough time to distinguish the difference between the single
note and the other octave notes.  If I had played the same passage slowly,
there would be little difficulty distinguishing the lack of the high octave
reed.

In regard my description below of the transfer of energy from the upper
partials to the fundamental, or first partial by cupping the harp,  I'm not
sure if this can be easily seen with Transcribe.  While working at Hohner
during the time that we were looking for a replacement for ZA-5 reed brass,
I used Spectrogram <http://www.visualizationsoftware.com/gram.html> to help
evaluate samples of harmonicas made with different reed materials.  With
Spectrogram, real time spectral analysis is possible of any sound input
through your computer's sound card.  For those interested in seeking more
information on accordion tone chambers, the other accordion term commonly
used for tone chamber is cassoto.

Best regards,
Rick

---------- Forwarded message ----------
From: Rick Epping <rickepping@xxxxxxxxx>
Date: Sat, Jun 28, 2008 at 1:09 AM
Subject: Re: Imaginary Hole Technique
To: Joel Thomas <theloveboxquartet@xxxxxxxxxxxxxx>


Hi Joel,
It's true that the amplitude of a harmonica reed's 1st harmonic can be as
high as that of its fundamental frequency.  However, there is more energy in
the fundamental frequency than in the 1st harmonic, so it's not quite
accurate to describe the 1st harmonic as being as strong as the fundamental,
if by strong you mean loud.  But the missing high F# frequency is certainly
there in the lower octave F# note.

Interestingly, if you play a harmonica note into the microphone of your
spectral analysis program with the harp uncupped, and then cup the harp, you
should see the amplitude of the harmonics decrease and that of the
fundamental increase, as energy is transferred from the harmonics to the
fundamental.  This demonstrates the principle of the tone chamber system
used in some of the more expensive accordions.

Best regards,
Rick