Do growls interact with the harmony?

Question

Is the pitch of growls measurable or is it undefined (for example: bass drum and hi hat are both unpitched but you can tell the relative pitch)? Both me and my friend have good ears and have been unable to tell the pitch that our vocalist is singing when growling, and I haven't found this topic raised anywhere on the internet.

EDIT: Reading a bit on wikipedia about unpitched percussion, I found the term 'inharmonicity' - in simple words it means that the sound produced doesn't interact with the harmony. I would like to know whether growls are harmonic or inharmonic, as it is possible to match pitch with growls but also with drums.

EDIT2: Another bit of information is that our vocalist sings in tune most of the time, with some chance of missing a few notes (when singing clean), but when he growls we can't tell wether he's in tune or not.

EDIT 3: Changed title from "Is growling pitched or unpitched?" to "Do growls interact with the harmony?", meaning, instead of if they have a fundamental pitch (Yes), if they interact with the harmony like clean vocals or don't interact with the harmony like drums (or somewhere in between like pizzicato which is both percussive and melodic).

Answer 1

Inharmonicity actually doesn't mean something doesn't interact with the harmony. It's only a measure for how strongly the sound deviates from a periodic signal (or equivalently, one with only integer-multiple sinuoid partials). Such periodic-signal sounds are particularly well-suited for interacting with harmony, but even very inharmonic sounds can, to some degree, do so (Gamelan music is pretty much entirely based on this). And vice versa, sounds with low inharmonicity can be used in a way that does not interact with the harmony (e.g. “siren” sound effects).

So, we really have two questions here:

1. Is growling inharmonic?

Well, there are different degrees of “growliness”, but all growling certainly has some inharmonicity, that's what distinguishes it from clean singing. But it's also not completely inharmonic (like e.g. a china cymbal).
To quantify this, look at a Fourier spectrum of a recording. For a clean voice, this will have well-separated peaks and nothing much else, roughly like^†:

^{Source: https://www.clear.rice.edu/elec431/projects95/psquared/psquared.html}
For a growled part there will be a much higher “noise floor” of inharmonicity, but I'm pretty sure you would still see some reasonably strong peaks, and they would probably still be spaced in integer ratio. Estimate sketch:

2. Does growling interact with harmony?

I think it can, in principle, but I don't really have evidence. I'd definitely say most metal singers don't use growling in a way that would interact with the harmony, and I don't know if you can even control the pitched components of growling in a way that would allow this. But if you sampled snippets of growled singing and triggered it with a keyboard to play, say, a Baroque cantata, I suspect it would sound more harmonious then you'd think (albeit completely weird).

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^†_{Spectrum analysers in music production are usually set up with logarithmic axes, which is more useful for mixing etc. purposes. But it means the spectrum will look inharmonic even if it's not: – the integer frequencies aren't equally-spaced anymore, and the noise floor appears much higher. If you try this out, be sure to set the spectrum to linear scale to properly see what's inharmonic and what's not.}

Answer 2

It's pitched because there is a core tone to a growl. Listen to what you hear the most of. Put the growl on a loop if possible. Sometimes if I'm really stumped on what a sound is, I'll take my tuner app that's on my phone and put it up to my speaker and I'll play the sound over and over until it picks something up.

When you think you've found the core tone, try to vocalize it and sing with the growl. There should be harmony. You could perhaps even try growling yourself and see if you can imitate the singer.