I've worked on a mini measurement setup to test out the maximum amplitude effect of playing a (digital) piano note through an artificial ambience program (on a Lexicon) and varying the diffusion parameter.



It's like playing the same note and changing the parameter, measuring the max output (let's say the "limit level") and making a table of the results. Like in the video but taking all the values gets this graph:



Intuitively, the more diffusion (effect mix of the ambience effect is 100%, no direct signal) the less amplitude. There is a matching resonance or something else that makes for a more interesting graph though.

The main point of the exercise was to test Midi connections (USB-traditional, all USB, Linux Jack, Linux Alsa based) and writing a simple application script to give midi commands and measure digital audio signals from a (Tcl) script. Also, I was trying to figure out the purity of the digital output, for instance I found out both the Lexicon Omega (only on *Linux*, I didn't test on windows for which there is an official driver) and an Asus motherboard (analog part blown) ALC based sound card TOS output both change the digital signal when I read it back in the Omega digital input.

I test that by setting up a digital connection, making a parallel software connection with a delay effect I know simply delays a number of samples, invert that signal, add the tos based input signal, and adjust the delay until the two cancel.

Also, the Midi on Linux interested me because on the Jack midi (for which I wrote a little example C program I used in the script in the video) side, there's sample accurate Midi messaging possible, which might be of interest to use with my FPGA experiments.

Anyhow, it's tiny bit boring an example, but possibly it can be imagined I can tune my complicated processing paths and also parameters of digital sound synthesis with these basic tools in a loop.

T.V