Lately I’ve been craving for more natural or real-world production methods in my music. What I mean by that is something like physical production. Plate or spring reverbs are one example: letting phenomena of the physical world influence recordings and tracks.
In the case of a plate reverb, a metal sheet is hung on a frame, two or more contact microphones (transducers) are attached to it and then the plate is brought into motion by a loudspeaker. The vibrations are picked up and amplified, delivering a super nice fake-reverb. It’s not a real room that’s reverberating, it’s a sheet of metal. You could say physical simulation.
Well, the same thing can be done with other vibrating, resonant object like for example… cymbals. Or piano strings, but that’s for another entry. The basic principle is the same like for plate reverb: attaching two piezo pickups to the cymbal edges and exciting them. Instead of exciting them with a loudspeaker, I choose to play the instruments in question directly next to them. Those contact mics have to be attached to a special piezo preamp and then mixed together with the dry signal.
The Piezos and Preamp
This is the piezo preamp I’m using for the reverb. It’s an own design and build and I describe it in detail in a different post. For now it’s enough to say that it changes the impedance of the piezos to be usable on a regular mixing desk and also provides a useful, adjustable hi-pass filter because you don’t want too much bass in your reverb.
Attached to it are little contact mics called piezos (from Piezoelectric sensor), they are basically disks that produce current when bent/pressed, so they need to be attached tightly to the surface that they are supposed to pick up. These piezos are dirt cheap, mine were around 1€ a piece.
This equipment is by its nature very susceptible to vibrations, handling noises, footsteps, so make sure to isolate the cymbal stand from the ground surface, but also the piezo preamp and cables leading to and from it! I did it by putting a little piece of cloth beneath the preamp and a big pillow beneath the cymbal stand. Otherwise it would pick up my neighbors footsteps. Oh well, at least there’s a lot of gain 🙂
In the sound example below, I play a regular flute next to two different cymbals (18″ Meinly Byzance Crash on the right and 20″ Zildjian Constantinople Ride on the left) and at 2:00 I switch to the microtonal Bansuri flute (indian bamboo flute). There’s some compression on the whole track as well as some (unfortunate) audio cassette hiss. Sorry about that. There are no other mics involved except for the piezos, which I would definitely change if doing a real recording. Anyway, you can hear two very distinct reverbs, with a lot of resonance coming from the various resonant modes of the cymbals. In some cases you can hear a saturation in resonance, which causes the cymbal to “overdrive” for a little period. Cool.
What I find interesting about this sort of thing is the non-linearity. As you play louder, the reverb doesn’t just get louder. Instead, the cymbal resonates more, is hit harder by the waves of sound, which in turn leads to it vibrating harder and thus creating more overtones (in general instruments produce more of the higher overtones, the harder they are played).
This non-linearity causes a huge increase in dynamics and a really wonderful, musical response in the reverb. At the same time, the reverb is not uniform: it accentuates certain frequencies way more than others, depending on the size, type and construction of the individual cymbals. That means I can change the signature of my reverb by changing the cymbal!
If you want, this is as close to analog convolution as you can get. One sound convolved on top of another while at the same time being a really dynamic sort of convolution.
Another example, a recording of an upright bass, this time with the addition of regular microphones, piezo reverb being mixed in rather loudly to make it a good example. I’ve used just one cymbal, both piezos placed on the edges. For a real mix, this would probably be too heavy a reverb. Realize how resonant the cymbal sounds with certain notes and also how it adds a pretty hollow color to it. Probably a bigger cymbal would suit the instrument better.
Anyway, I hope I got you inspired. In another post I explain the construction of the preamp as well as provide schematics so the DIYers among you can build their own. In yet another post I’ll expand upon this idea and stick the piezos inside my grand piano, lift the pedal… in order to create a really incredible, long, harmonic reverb.
Love the physical world.