When thinking about instruments…

People often look at the melodeon (or indeed any instrument) and claim that a particular part is good for the sound. For example, people sometimes (erroneously) say that resonance of the palletboard improves the sound of the instrument.

Whenever I hear something like this, I run through a little checklist of questions in my head. If all three result in a tick, then all well and good. Mostly though, at least one has a cross by it and often one ends in a question mark.

  1. Is there a mechanism? Meaning, can you see a physical way in which this might happen? In the case of palletboard resonance, it is true that the palletboard will doubtless have some resonances associated with it. However, in contrast to say a guitar, these resonances will probably be very high in frequency and low in amplitude, due to the clamped edges and the presence of the reedblocks effectively limiting the area free to vibrate. I showed last week that some vibration does pass through into the palletboard, so it is conceivable (but see point 3) that the reed could drive the palletboard to resonate.
  2. Is it desirable? There is no point extolling the virtues of a part if the mechanism that you are talking about detracts from the sound rather than adds to it. To continue with our example, there is a significant difference between free reed instruments such as the melodeon and plucked stringed instruments such as the guitar. The sound of the guitar that you hear is not that of the strings – they are a poor radiator of sound. Instead, it is the physical movement of the front (and to a lesser extent and at low frequencies, the back, sides and cavity), which passes the sound information on to the user. So the characteristics of the front, including its resonant frequencies, are very important in a guitar. In a melodeon though, the sound is generated by the interruption of an airstream – nothing to do with the palletboard at all. Palletboard resonance would, in fact, take energy away from the vibration of a reed, making it more indistinct. In addition, having an appreciable movement of the palletboard could drive the reedblocks to vibrate, which is a recipe for some horrible sounds. Even if the palletboard did resonate, it would likely be at such high frequencies that it would be inaudible anyway. So I am pretty convinced that resonance of the palletboard, if it did occur, would be a Bad Thing.
  3. Is it noticeable? This is a really crucial question. Having identified a mechanism and worked out whether it is desirable or not, we must now work out whether we’d actually be able to hear the difference. In this case, I am satisfied that the energy from the reed is not sufficient to drive the palletboard to resonance, unless the structure of the box was radically changed. The vibrations entering the palletboard are so small in amplitude that the prospect of resonance is pretty much non-existent.

[To continue our example briefly, by showing that palletboard resonance is undesirable and won’t happen anyway, I am not saying that it can’t affect the sound. I showed last week that it is conceivable that it might do through travelling waves (although I have yet to answer point 3 or indeed point 2 in that respect), but it should also be stated that the thickness of the palletboard would alter the airway to the reed (although I have yet to answer points 2 or 3 for this as well).]

I find those three questions – the mechanism, the desirability and how noticeable it is – to be very useful tools in analysing instruments. At the very least it will challenge your conceptions by asking you to explain yourself. And at the most it can lead to new insights about the instrument. It is a good way to start to think scientifically about instruments, rather than anecdotally.

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3 thoughts on “When thinking about instruments…

  1. :-) Most pallet boards on the bigger boxes (and accordions) are plated up with an Aluminium plate on the pallet side anyway, basically removing most possibilities of any resonance in any direction :-)

  2. Pingback: Box Acoustics Primer Part 1 – An Overview | Music and Melodeons

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