What a good question! I am actually asked this question often during a presentation I give, and it is usually raised after I talk about the unique requirements of string instrument players.
My own clarinet and a violin can generate rather similar looking spectra- they both have much of their energy in the lower frequency region and, like the long-term average speech spectrum, the spectra fall off at about 6-8 dB/octave. Nevertheless, it seems that a violinist, or someone who likes to listen to string instruments, has a substantially different perceptive requirement from someone listening to woodwinds (e.g., clarinet, saxophone).
When I play my clarinet, or equivalently when someone listens to a clarinet and they comment that it sounds great (quite rare for my clarinet playing, by the way), they are referring to the lower frequency inter-resonant breathiness. That is, I can chop off all sound energy above around 1500-2000 Hz and it still sounds great- there is an emphasis in the lower frequency region.
In contrast, when a violinist, or equivalently when someone listens to a violin and they comment that it sounds great, they are referring to the balance between the lower frequency fundamental energy (the name of the note being played) and the relative sound level of the higher frequency harmonic energy. That is, unlike a woodwind, what is important to play and hear with a stringed instrument is a broad-band signal that includes the lower frequency fundamental energy AND the higher frequency harmonic energy.
My clarinet and someone else’s violin may generate similar sound energy spectra, but what is important to hear is an entirely different ball game. A clarinet may have as much high frequency spectral sound energy as a violin; it’s just that nobody really needs to hear it.
One can therefore argue that the “best” hearing aid for a string player, or someone who likes to listen to string music, should be a single-channel device where the lower frequency fundamental energy and the higher frequency harmonic energy are treated similarly in the same channel of a hearing aid. String music is ubiquitous in the classical domain but less common in other music types such as jazz and rock.
For woodwinds, brass, and percussion, and, I suspect (but am not sure), for amplified guitars, hearing aids that can handle the lower frequency fundamental energy and the higher frequency harmonic energy in different bands (e.g., a multi-band compression hearing aid) would be fine.
In classical music where there is a strong emphasis on string music (perhaps not a Wagnerian opera?), less may be more; a single-channel hearing aid would be the way to go.
Unfortunately, there are no single-channel hearing aids on the market (other than the K-AMP, which I understand is still available from www.GeneralHearing.com), so perhaps hard of hearing string players are stuck with less than optimal amplification.
There are ways to simulate some aspects of a single-channel hearing aid, and although these techniques are not perfect, they may be able to improve the situation for playing and listening to string-heavy classical music. The easiest way is to set all compression elements in all of the channels identically: same compression ratios, same attack and release times, and same threshold kneepoints. This is not the same as a single-channel system, but given that the lower frequency fundamental energy is occurring at the same time as the higher frequency harmonic energy, the “one-channel simulation” would not be bad. This would not work for speech where one phoneme (such as /a/) would occur “before” the next phoneme (such as /s/), but for music, which is a much more “simultaneous” signal, this simple programming strategy may be useful.
I don’t really see a downside of this programming strategy for other forms of music- it may not be as important for non-string heavy music but, like chicken soup, it can’t hurt.
And like some of my previous blogs, this is based more on my clinical experience than on a well-defined research project. This would make an excellent Capstone essay for any graduate student to study in more depth.