So, I ended up concluding this kind of exploration would probably be largely a waste of time. But in the process, something else caught my eye to which I previously paid scant attention: the ability to export/import additive specifications (.aaz files in Alchemy-speak) as text files (.csz files) that can even be loaded into Excel. But here's the thing about CSZ files: they're massive, with huge numbers of data points. You wouldn't even think about doing manual tweaking. And while they can be loaded into Excel, if you tried programming meaningful Excel value manipulation, you would surely end up with a spreadsheet from hell. But, there's another possibility here and that's the direction I went ... with gratifying results at the end of the day. What about creating software that would generate Alchemy CSV files? The strategy would allow introducing randomness to achieve the desired serendipity in a controlled way that can produce usable, interesting sounds. Fortunately for me, my day job is that of a software engineer, so the programming skills required are no big deal and I had a rare opportunity to use them for something genuinely fun. Thus was born the Addulator, an Alchemy CSV file generator that I'll be making freely available to fellow Alchemists.
Adding It All Up Let's begin with some background on additive sound generation. Consider the characteristics of a standard saw wave. To create one with a frequency F from sine waves, we need a component sine wave with frequency F, a second with frequency 2*F (exactly), a third with 3*F (exactly) and so on ad infinitum. Each of the partials has a phase of zero (in other words, they all start at the beginning of the sine wave cycle). Finally, each partial has amplitude of 1/PN, where PN is the partial number, resulting in a continuous attenuation of sine wave amplitudes as the partial number increases. Now, a pure saw wave is pretty bright (you might call it "buzzy"), and when used in subtractive synthesis, it's often heavily filtered. We could go brighter still by attenuating higher partial amplitudes less, but at some point there'd be so much high frequency content that the sound would be flat-out irritating. Keep that in mind further on. Next, what happens if we start changing the amplitudes of partials? As we do so, the saw wave shape starts to distort. If we continuously change the amplitudes on the fly, we have a situation equivalent to changing the resultant base waveform as often as every cycle.
August 2012
But it gets more interesting when we change the phase of partials. Gradually changing the phase of a partial changes the pitch during the period of transition. Conversely, introducing a gradual pitch change from the initial to a different pitch and then back to the initial will result in a partial with a new phase (in relation to that of the fundamental) when the transition is complete. Throw in L/R pan position changes in the partials and we've got something akin to an Alchemy additive sound specification. Using continuously varying partial parameters, we can achieve the equivalent of having a single cycle oscillator that can change the wave form as frequently as each individual cycle while changing the stereo image at the same time. But we can't just throw random numbers into the mix and expect a musical sound. The changes can't be too jagged or extensive and rapid unless we want a really chaotic sound to begin with. Furthermore, pitch deviations too far from a multiple of the fundamental pitch will produce enharmonic results (again, not good unless that's what we're shooting for in the first place). It all boils down to this. We want serendipity, but it needs to be governed by some reasonable constraints.
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