I had the idea of live sampling my tuba for an upcoming gig. I've had this idea before but never used due to two major factors. The first is the difficulty of controlling a computer and a tuba at the same time. One obvious solution is foot pedals, which I've yet to explore and the other idea is a one-handed, freely moving controller such as the wiimote.
The other major issue with doing tuba live-sampling is sound quality. Most dynamic mics (including the SM57, which is the mic I own) make a tuba sound like either bass kazoo or a disturbingly flatulent sound. I did some tests with the zoom H4 positioned inside the bell and it appeared to sound ok, so I was going to do my gig this way and started working on my chops.
Unfortunately, the sound quality turns out not to be consistent. The mic is prone to distortion even when it seems not to be peaking. Low frequencies are especially like to contain distortion or a rattle which seems to be caused by the mic itself vibrating from the tuba.
There are a few possible work arounds. One is to embrace the distortion as an aesthetic choice and possible emphasise it through the use of further distortion fx such as clipping, dropping the bit rate or ring modulation. I did a trial of ring modulating a recorded buffer with another part of the same buffer. This was not successful as it created a sound lurking around the uncanny valley of bad brass sounds, however a more regular waveform may work better.
At the SuperCollider symposium at Wesleyan, I saw a tubist (I seem to recall it was Sam Pluta, but I could be mistaken) deliberately sampling tuba-based rattle. The performer put a cardboard box over the bell of the tuba. Attached to the box was a piezo buzzer in a plastic encasing. The composer put a ball bearing inside the plastic enclosure and attached it to the cardboard box. The vibration of the tuba shook the box which rattled the bearing. The piezo element recorded the bearing's rattle, which roughly followed the amplitude of the tuba, along with other factors. I thought this was a very interesting way to record a sound caused by the tuba rather than the tuba itself.
Similarly, one could use the tuba signal for feature extraction, recognising that errors in miccing the tuba will be correlated with errors in the feature extraction. Two obvious thing to attempt to extract are pitch and amplitude, the latter being somewhat more error-resistant. I've described before an algorithm for time-domain frequency detection for tuba. As this method relies on RMS, it also calculates amplitude. Other interesting features may be findable via FFT-based analysis such as onset detection or spectral centroid, etc using the MLCD UGens. These features could be used to control the playing of pre-prepared sounds or live software synthesis. I have not yet experimented with this method.
Of course, a very obvious solution is to buy a better microphone. It may also be that the poor sound quality stemmed from my speakers, which are a bit small for low frequencies. The advantage of exploring other approaches include cost (although a tuba is not usually cheap either) and that cheaper solutions are often more durable or at least I'd be more willing to take cheaper gear to bar gigs (see previous note about tuba cost). As I have an interest in playing in bars and making my music accessible through 'gigability,' a bar-ready solution is most appealing.
Finally, the last obvious solution is to not interact with the tuba's sounds at all, thus creating a piece for tuba and tape. This has less that can go wrong, but it looses quit a lot of spontaneity and requires a great deal of advance preparation. A related possibility is that the tubist control real-time processes via the wiimote or other controller. This would also require a great deal of advanced preparation - making the wiimote into it's own instrument requires the performer to learn to play it and the tuba at the same time, which is rather a lot to ask, especially for an avant guarde tubist who is already dealing with more performance parameters (such as voice, etc) than a typical tubist. This approach also abandons the dream of a computer-extended tuba and loses whatever possibilities for integration exist with more interactive methods. However, a controller that can somehow be integrated into the act of tuba playing may work quite well. This could include sensors mounted directly on the horn such that, for example, squeezing something in a convenient location, extra buttons near valves, etc.
I'm bummed that I won't be playing tuba on thursday, but I will have something that's 20 minutes long and involves tuba by September