Sound Design - Cymbal Soup

THE INGREDIENTS

To make our sound, we began with a bowed cymbal. Pulling a violin bow across a cymbal results in a wonderful effect. It begins the cymbal gently resonating, exciting its surface with a specific pitch. It is an eerie and complex sound, different than the un-pitched crash typical of the instrument when it is struck. Imagine it as the distant, spooky cousin of the sound made by running a moist finger around the rim of a wineglass.

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Every cymbal creates a different pitch when it is bowed, so we began the expedition bowing each of our cymbals to find the one which had the richest sound. As you will soon see, we were looking for exaggerated stereophonic material with high frequency content that would provide rich material for the processing to come (read on!).

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THE TOOLS

After settling on a medium sized crash cymbal we proceeded to set up a pair of microphones in what is known as an M-S (or mid-side) array. In short, this is a stereo mic technique that simultaneously employs two different kinds of microphones: The first is generally a “cardioid” microphone, meaning that it is sensitive mostly to whatever is directly in front of it. This mic is pointed directly at the sound source. However, the second microphone has a bi-directional (or figure-eight) polar pattern, meaning that it “hears” from the front and back but not the sides. It is placed closely as possible to the first mic, but ninety degrees to the cardioid mic; pointed perpendicular to sound source. One advantage of this configuration (after a bit of phase canceling trickery) is that one can adjust the balance between the two mics, dramatically changing the perceived depth of the stereo image.

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Using the MS pair, we recorded the stereo cymbal as widely and as openly as we could in an effort to imbue it with an artificially vast amount of space. Noticing that a cymbal's sound is very different on the top and bottom so we placed our M-S pair so that the figure-eight mic was level with the cymbal but “listening” directly to the sound from above and below it instead of from side to side. Because of what would happen next, we wanted to capture as much of the high frequency information as possible. So in an attempt to catch sounds that only bionic dogs might hear, we recorded this sound at the super-sonic sample rate of192 kHz.

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SIMMER AND SPICE TO TASTE

With a fresh, new cymbal sample waiting to be mangled, we created a new song document in Apple's Logic Pro. This session, however, we slowed down to conventional "CD quality" (a sample rate of 44 KHz). This effectively brought all those wonderful “dog overtones” down into the realm of human hearing. The resultant sound, while still recognizable as a bowed cymbal, also had a beautiful, dark and mournful pitch, rich with evolving overtones and expansive spatial cues.

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Although we now had an interesting sound which might have afforded us good underlying flavor, we were not done. Opening our creation in Logic's “Space Designer” plugin provided the finish for this effect. Space Designer is a convolution reverb. It works by taking an acoustic “fingerprint” of a space, and applying it to another sound. Typically, reverberant spaces such as halls, cathedrals, and rooms are sampled in order to give the impression that a recording made elsewhere had been made in one of these beautiful echo-y spaces. Thankfully there is no rule that states one must actually use a reverb impulse to drive Space Designer. Convolution reverbs can be loaded up with absolutely any sound one might imagine as a fingerprint: a reverberant space, a guitar amp, or in our case, an exquisitely dark and spacious bowed cymbal.

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And it paid off. Our new impulse immediately gave us the results we were after. Passing a single piano note through the fingerprint of a cymbal resulted in a fascinating sound, eliciting the evolving character of the bowed cymbal, but with haunting musical pitch. What's more, although the piano note was short, (less than 1 second long), the reverb yielded a long pad due to the fact that the convolved cymbal was about 30 seconds in length!

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CONCLUSION

With our pad all good to go, we were ready to add more ingredients to this sonic soup. The underlying “stock” would present both a compositional element and inspiration help us complete the composition. In the accompanying example, you will hear strings, piano, and celesta...and even if one isn't overtly aware of it, it is the underlying sound we created that holds it all together. When it was done, the sound provided a latent sense of movement and mood to a piece that could not have been achieved in any other way. In all, the sound design for this song was a great time, imbued with playful experimentation, all the while guided by our bowed cymbal.