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Are the highest pitches always the easiest to hear in a musical texture (all other factors, such as dynamic, timbre, articulation, etc. being equal)? Is this why melodic parts tend to be the highest part within a musical texture (or certainly higher)?

Presumably inner parts of a texture are always harder to hear; despite its obvious importance (in terms of perceiving harmony), is the bass part always as easy to hear as a melody part?

How is this affected by overall register? (For instance, if all parts are higher or lower.) Or by spacing? (If there is a greater distance between parts of a musical texture.)

If higher tones are easier to hear (within a musical texture or not) why is this?

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5 Answers 5

In short: no. Obviously, you don't hear bats. But actually the main problem with your question is that you write "all other factors, such as dynamic, timbre, articulation, etc. being equal". "dynamic" is a diffuse term usually implicating loudness, and similar loudness will be similarly noticeable. "timbre" contains the composition from harmonics and that implies a set of frequencies. It's not independent from pitch.

The usual fundamental frequency typically has several diminishing harmonics. The bulk of the harmonics, even for the highest instruments being played, are within reasonably well-audible frequencies. So the harmonics of high notes are nicely spread out and have the higher frequency ranges mostly to themselves.

That gives them an advantage. There are lots of ways in which tones can be made to "cut through". Accordions use "tremolo", several reeds slightly out of tune with each other. The resulting beating is very regular and this very discernible even compared with similar (unsynchronized) notes. Things like high-hats plaster over a large part of the high frequency spectrum with a common dynamic, again standing out as a unit. Percussive instruments (this includes non-bowed string instruments) have common envelopes for their frequency imprint. Singers and wind instruments have a characteristic spread of "formants" which are frequency envelopes not moving with the fundamental pitch itself.

So like in a pencil drawing which just consists of lines and actually pencil marks, there are lots of cues which help with piecing things together and offsetting them from other elements. High pitches tend to be "well-lit" in the sound texture. But for example the whine of a CRT tube or (these days more likely) a switching power supply, in spite of being high, is hard to discern because it has few audible harmonics and no detectable changes of volume.

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Laptop switching power supplies tend to be much more audible than I'm happy with... not acoustically, but electrically, interfering with instruments plugged into an audio interface without galvanically separated ground. –  leftaroundabout Aug 7 at 0:31
    
+1 @user12938, thanks for pointing out the deficiencies in the question, too! –  Bob Broadley Aug 7 at 13:46

I don't know about 'easier to hear', within a well produced piece of audio, you should be able to hear everything.

Within a chord though, for example, I associate the highest note of a chord as the 'one that stands out'.

I have made two short quick examples of "Twinkle, Twinkle, Little Star" to demonstrate what I mean. (I used the first online sequencer I could find, I'm really unfamiliar with it, I hope it works - I have a very basic setup so I hope they do. If not, I'm sorry - perhaps a project for meta might be to get something we can embed more easily into questions and answers, like how chess.stackexchange.com have an embeddable game playback viewer).

The first example, the tune is played with chords where the highest note of each chord also belongs to the melody: http://onlinesequencer.net/20687 (midi version) - and this sounds about right.

The second example, the tune is played with chords where the lowest note of each chord plays the main melody: http://onlinesequencer.net/20693 (midi version) - which, to me, is barely recognisable, and more suitable as a harmony/accompaniment for the melody, for the left hand.

(Un)scientifically, I think two frequencies of the same sound (so, same instrument) with the same amplitude will vibrate the same amount of air, for a single sound wave length (possibly not the same because the thing that produces the lower frequency is vibrating more slowly). A higher frequency sound has a shorter wavelength, so you would expect it to vibrate more air because it is moving at a faster rate. Whether this is compatible with the mechanics of hearing, I don't know, but within the pitch-range of a musical instrument, the higher notes of chords appear to be heard more prominently.

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Yes, some frequencies are easier to hear. We tend to be specially sensitive to frequencies around 2000 and 5000 hertz. The resonance of the ear canal and the transfer function of the ossicles of the middle ear cause of this phenomenon.

We see this measured in equal-loudness contour charts, a study first performed by Harvey Fletcher and Wilden A. Munson, which will be later known as the Fletcher–Munson curves. Other measurements have been performed since then, and some flaws were found in the Fletcher-Munson measurements. Current equal-loudness contour charts, when compared to the Fletcher-Munson curves, are very different in some ranges, specially in the lower half of the spectrum.

Fletcher-Monson curves

We can see that our sensitivity peaks at around 4kHz, so it'll be easier to hear frequencies from around that range. We also see that it's not the case of "the higher the easier", as the sensitivity will decrease as we go past 5kHz.

Another thing to notice is that as the sound intensity becomes higher, the differences become smaller. At low amplitudes the differences are much bigger than at higher amplitudes.

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+1 Thanks for this info, JC! Any thoughts about a musical texture with several parts all around the frequencies we are most sensitive to? –  Bob Broadley Aug 7 at 13:44
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@BobBroadley If they all are so close together (that's around a one octave range) I feel like the note with less masked harmonics will be easier to hear, which would still be the highest one. I wanted to include that dynamic in my answer, but I can't find an article/study/paper about it, so I'm not sure if that idea is correct. I still feel like both are important in why the exposed high note is so important (and this last piece could also explain why the low exposed note is so important too). –  JCPedroza Aug 7 at 20:40

Are the highest pitches always the easiest to hear in a musical texture (all other factors, such as dynamic, timbre, articulation, etc. being equal)?

I guess when you put it that way, "all other factors", I would say the upper and lower voices are easiest to hear.

That said, there are a number of factors that I find to be very important whether a line in a texture is perceived as "salient" and that is rhythm and pitch content.

If the upper and lower voices are more slowly paced, and have the same rhythm then a faster paced inner voice will stand out, in particular when it has varied pitch content (as opposed to a repeated figure). Also, if the inner voice has a lot of dissonance and the outer voices use mostly consonants then the inner voice will also be distinguished by the use of dissonance.

However in many cases the upper line will also be more interesting in both rhythm and pitch content.

is the bass part always as easy to hear as a melody part?

If you put it this way, "always", then I would say no. It is very often the case that the lowest voice tends to move by leaps or at least larger leaps than the inner voices. That contributes a lot to how clearly you can hear it. If you would set up a texture where the lowest voice uses about the same contours as the inner voices, then it becomes less distinctive.

Another thing that often happens with the lowest voice is that there tends to be more space between the lowest voice and the lowest of the inner voices than between the inner voices themselves. This spacing also helps you to distinguish the lowest voice more clearly within the texture. So if the lowest voice is narrowly spaced then that will take away some of its prominence, possibly enough to allow an inner voice to be heard more clearly.

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+1 Thanks for this RB, I anticipated mostly getting answers related to acoustics, which I think I will, so it is good to get a "compositional"(?) perspective, too. –  Bob Broadley Aug 7 at 13:46
    
Bob, you're welcome! –  Roland Bouman Aug 7 at 22:26

I'm too lazy to look up references, but my understanding is that there appears to be a psychological phenomenon that amplitude and pitch are both factors of a sense of intensity. With two pitches at the same amplitude: the higher one will appear to cut through the lower. Pragmatically, a Bass will need a lot more air to compete for volume with a Soprano.

But it is my understanding that this is a psychological effect, not directly reducible to a physical explanation.

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Fletcher-Munson effect: we're more sensitive mid-high (1k-10k Hz) frequencies of sound en.wikipedia.org/wiki/Equal-loudness_contour –  Dave Aug 6 at 17:38
    
Thanks, Dave! I was wondering when you'd chip in with an answer to this! Any chance you could put this in a full answer? –  Bob Broadley Aug 6 at 17:57
    
But it is my understanding that this is a psychological effect, not directly reducible to a physical explanation. It is physical effect, since it's caused by the resonance of the ear canal and the transfer function of the ossicles of the middle ear. –  JCPedroza Aug 6 at 20:19
    
It is a physical stimulus of course, but a psychological response. The Fletcher-Munson measurements, and the subsequent refinements AFAICT are based on reports from human subjects. It can be correlated to physically measurable features of the stimulus, but the effect itself transpires in the hearing and not in the physics. –  luser droog Aug 9 at 8:48

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