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Tuning the double reed harmonicas

"More art than science" is a somewhat cliched phrase, but it is also a rather apt description of the process of tuning the double reed harmonicas. (For more about double reed diatonics, please refer to this page.)

Octave harmonicas have one set of reeds tuned one octave below the other set and present fewer challenges than tremolo harmonicas, the main thing to keep in mind is that lower pitched reeds tend to flatten more with increased pressure than higher pitched reeds. This means that you may need to tune the lower pitched reeds a little sharper than their higher tuned partners, although this is not really much different from checking and tweaking the octaves on a single reed diatonic.

Tremolo harmonicas can be a little less straightforward. Not only do you have to get the individual notes of the instrument sounding in reasonably good tune, you also have to deal with the tremolo effect itself. Usually tremolo instruments are tuned so that the beating effect gets faster as you go higher up the instrument. It is possible to tune so that the tremolo rate remains constant across the full range of the harmonica, but this has some negative effects on the basic tuning of the instrument. For example, in order to get a tremolo of 8Hz (ie eight beats every second) at the note C7 (the C three octaves above middle C), you would need to tune them about 7 cents apart. However, in order to get a tremolo of 8Hz at middle C, you would need to tune the notes about more than 50 cents apart. 50 cents is a quartertone (ie one half of a semitone) - although the rate of the tremolo might be pleasant, the effect of playing two notes tuned a quartertone apart would be considerably less pleasant.

The degree to which the two set of reeds are tuned apart and the resulting intensity of the tremolo effect produced is described as "wetness". In a perfectly dry tuning, the two reeds are tuned to the exact same frequencies and there is no tremolo effect at all. Some harmonicas have been produced this way and they were often described as being in "Band Tuning". The greater the distance between the tuning of each set of reeds, the wetter the tremolo, although there are no standardised terms for the various degrees of wetness.

This table gives "serving suggestions" for six different degrees of wetness, with the tuning offset in cents and the rate of tremolo in Hertz (beats per second) for the notes C4 (middle C), C5 (one octave above middle C), C6 (two octaves above middle C) and C7 (three octaves above middle C). Please do not take these figures too literally - it's not really possible to tune a harmonica reed to within one quarter of a cent. However, this should give you some idea of how to set up a tremolo tuning. Clicking on the loudspeaker button will play an audio clip of each example.

5c / 0.75Hz
4c / 1.25Hz
3.25c / 2Hz
2.5c / 3Hz
10c / 1.5Hz
8c / 2.5Hz
6.5c / 4Hz
5c / 6Hz
15c / 2.25Hz
12c / 3.75Hz
9.75c / 6Hz
7.5c / 9Hz
20c / 3Hz
16c / 5Hz
13c / 8Hz
10c / 12Hz
25c / 3.75Hz
20c / 6Hz
16c / 10Hz
12.5c / 15Hz
30c / 4.5Hz
24c / 7.5Hz
19c / 12Hz
15c / 18Hz

That covers the basic theory, so let's move on to some practical stuff.

Most Western-made octave harps have the lower octave reeds on the top reedplate and the upper octave reeds on the bottom reedplate, although Asian-made octave harps are often built the other way around. Usually, I tune the higher pitched set of reeds first, then tune the lower pitched reeds. Finally, I double check the tuning with the instrument fully assembled and make any necessary adjustments. When checking each pair of reeds together, listen carefully for beating. If the beats speed up when you increase the air pressure, then the octave is slightly wide - ie either the lower note is a little flat or the upper note is a little sharp. If the beating slows down when you increase the pressure, then the octave is slightly narrow - ie either the lower note is a little sharp or the upper note is a little flat. For fine tuning the blow reeds with the reedplates attached to the comb, I usually use a small battery powered drill fitted with a tiny engraving bit and work through the slots from the outside of the reedplate. This makes the job much easier, especially when working on those harmonicas with nailed-on reedplates. Don't use a high powered drill, as you can very quickly cut right through the reed.

European-style tremolo harps most often have the concert pitch reeds (technically known as the foundation row) on the top reedplate and the tremolo reeds (i.e. those tuned slightly sharp) on the bottom reedplate and Asian-style tremolos are usually set up the opposite way around. However, this is not a hard and fast rule and there are plenty of exceptions, so it's best to check your harp against a tuner before starting work. Actually, this is good advice with regard to any type of harmonica - it helps to get a sense of the task that lies ahead.

I usually tune tremolo harps in a similar way to octave harps, i.e. tune the foundation row, then tune the tremolo reeds, then double check everything with the harp fully assembled. An alternative way of setting up the tremolo is to pick an imaginary centre point, then tune one set of reeds slightly higher and the other set of reeds slightly lower. In practice, I'm not sure that there is really much to be gained from this approach.

One problem with tuning tremolo harps is that the pitch of a reed tends to be slightly influenced by the pitch of the reed that is paired with it. This means that if you tune a reed in isolation, when its partner reed is allowed to sound the pitch of the first reed can change a little. Again, most of the time this effect is negligible or can be easily corrected by ear when you do the final touching up of the tuning, but on the Suzuki Tremolo Chromatic this can be a significant issue due to the way the SCT is constructed. One way to save a lot of frustration is to use a tuner that allows you to monitor the pitch of two reeds simultaneously. There do not seem to be many tuners capable of doing this, but one that can do it and does it very well is Dirk's Instrument Tuner. Although I am generally not a fan of computer-based tuners, this one is excellent, allowing you to set a desired degree of tremolo and check two simultaneous tones over a very wide pitch range. I am in no way affiliated with the author of this program, but if you intend to tune a lot of tremolo harmonicas, this will make the task much easier.

Aside from the above points, tuning the double reed harmonicas is not too different from tuning single reed harmonicas and issues such as temperament are dealt with elsewhere on this site.

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