Typical overtones?

Ok, I'm pretty sure, if I keep scouring the web for this information, I'll be looking forever.

I'm trying to find out, without buying a bunch of instruments and spending a few months analyzing their sound, if there are specific overtone frequencies associated with every instrument. For instance, does a violin made by one manufacturer contain the same overtones as one made by a different manufacturer when playing a C5?

Every single sound has a different set of overtones, or different dynamics of each overtone.

When you hear a sound, the frequency you hear most strongly is the fundamental (which gives out the "pitch" of the sound), and the timbre of that sound is determined by its overtones and the amplitude of each single overtone.

Some overtone series are pretty normally distributed (so, for example, the amplitudes of the flute overtones are pretty much regular - the higher the overtone, the lower the amplitude, while the clarinet follows a different pattern, so some higher overtones are louder than some of the lower ones).

Therefore, two different violins would have a more similar than not type of overtones (i.e. the overtones would be quite similar, and the pattern of dynamic levels too), but never the same. In fact, you're very likely that never in your life will you hear a tone that is exactly the same as something you've heard before; every single time it will be oh so infinitesimally different.

First two google results for "overtones instruments" give:

Harmonics and Overtones: The Fundamentals and Beyond...

and

Overtone - Wikipedia, the free encyclopedia

But you can find more info here too, and if I had access to the school's library from home I'd recommend you a book, but I don't so I'll do that tomorrow.

It should also be noted that it's pretty much impossible to just name the characteristics of the overtone spectrum of an instrument quickly. A certain tone may indeed have characteristic overtone amplitudes, but this doesn't alone depend on the instrument, but also a lot on the loudness, pitch and technique you are playing the instrument on, as well as on what part of the tone you are looking at. (The spectrum of a played tone doesn't stay the same from start to end: It is vastly different at the attack, i.e. when you start playing the note, during the sustain phase, and in the decay.)

So even just a single violin, playing a C5, might produce a great variety of different overtone spectra. This also means that just a single overtone setup is in many cases not sufficient for us to determine by what instrument it's being played. What we listen to is also how this setup develops over time, how it reacts to loudness changes, etc. Two violins will show a relatively similar behaviour there, which is why we can reckognize them as violins, but as Jujimufu said, no two instruments or tones are ever the same.

P.S. Well, to be precise, you are right that two violins contain the same overtones (considering they are built normally), i.e. the harmonic series. The difference lies in the loudness of each overtone. There are only a few instruments that have fundamentally different overtones (like bells, which have inharmonic spectra), and a few instruments that have certain overtones very much suppressed (like clarinets, which have almost only uneven overtones).

Therefore, two different violins would have a more similar than not type of overtones (i.e. the overtones would be quite similar, and the pattern of dynamic levels too), but never the same. In fact, you're very likely that never in your life will you hear a tone that is exactly the same as something you've heard before; every single time it will be oh so infinitesimally different.

This is pretty much what I was assuming but I couldn't find any confirmation.

It should also be noted that it's pretty much impossible to just name the characteristics of the overtone spectrum of an instrument quickly. A certain tone may indeed have characteristic overtone amplitudes, but this doesn't alone depend on the instrument, but also a lot on the loudness, pitch and technique you are playing the instrument on, as well as on what part of the tone you are looking at. (The spectrum of a played tone doesn't stay the same from start to end: It is vastly different at the attack, i.e. when you start playing the note, during the sustain phase, and in the decay.)

The reason I was asking is because I've been getting more and more interested in a spectral approach to composition. I figured, if I could look at a spectrogram of an instrument and assume that it would contain the same overtones, regardless of the make of the instrument, I could make very clear decisions about how to blend other instruments with it.

For instance, I could have a violin play that C5, check the overtone frequencies, and have a flute come in by playing the pitch of one of those frequencies. According to what you two are telling me, this would be all but pointless because the next violin to play that same note won't have overtones that translate to the same pitches.

No, that wouldn't be pointless at all. First of all, as I said, the pitches of the overtones are pretty much same for all those instruments, the difference lies only in how loud each of them are and how this loudness develops over time. The overtone frequency you find in the spectrum of one violin will also be in the spectrum of another violin, and even an oboe or trumpet, just the strength will vary a bit.

And the difference between two violins definitely exists (otherwise we couldn't tell two violins apart), but it's very small, compared to the difference between two different types of instruments. For instrumentation-matters such as this, it shouldn't matter. Here only questions like loudness or special bowing techniques make a big difference.

Your approach should work well enough.

You should check the work of the so-called "Spectral" composers, such as Murail and Grisey (and Harvey, for that matter - I really love his Mortuos Plengo) - they investigate exactly that matter, how to incorporate elements and characteristics of the overtone of instruments, sounds, noises, tuvan throat singing or whatever, and then implement that in the orchestra.

And you should definitely check SPEAR, a program that analyses a given audio file (AIFF, WAV etc) and re-creates a virtual "sonic" representation of it by creating sine-waves of certain frequencies and amplitude for each fundamental and harmonic/overtone for the whole audio file. And from there on you can do all sorts of editing and manipulation, such change dynamics, pitch, length, move certain partials, delete some others, stretch some while contract some others - basically it allows you to visually interact with the sonic material on your screen by being able to drag-and-drop anything anywhere, and choose and manipulate every single partial at will (although they're not the actual partials of the audio file, but a sine-wave representation of them - so the sonic result will be very close but not quite the same as the original audio file).

This thread might be of use: http://www.youngcomposers.com/forum/fourier-analysis-intruments-15831.html