E 16′ s “Retriggering Function”

 

BASIC STEP SEQUENCING IN MAX/MSP

Once I defined the “buffer~ ” and “groove~”  as the patch’s storage and playback source, I had to deal with actual playback. I went straight for the following combination of objects:

  • metro”, as the sequence clock source
  • counter”, that outputs numbers within a specific range (e.g. counter 1 16) at the tempo set by “metro”
  • select”, that fires a bang from its outlet matching the input value

I opted to use a single “select” because it helps me to keep the patch tidy.
Thus, the “counter” ’s output count is routed into one “select” object that looks like this:
[sel 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16]
In this case, such object has 17 outputs; one per number, plus an additional one that outputs values which do not match its argument.

I used “select” in combination with various gates, that handle manual step activation and deactivation.
“select” fires a bang at each count; if the gate is open, the bang reaches the trigger button of the sample playback. Otherwise, the bang gets rejected and playback isn’t triggered.

THE RETRIGGERING FUNCTION AND THE INFLUENCE OF FM SYNTHESIS

It is at this early stage that I started wondering about what could make my instrument unique.

In this moment of my life I’m very much into FM synthesis, which got into my way extensively while building LMNC’s Super Simple Oscillator . At one point I thought: “why don’t I patch it into the Crave’s pitch CV input?”… and here I discovered “analog FM”.

Since then, I got fascinated by modulation at audio rate, which pushed me to make some “FM experiments” in Max/Msp.
Unfortunately the quality of the sounds generated in Max is not very good, thus I started thinking about a way to synthesize FM-ish sounds out of samples.
It didn’t take long before I came up with the solution… retriggering samples at a very fast rate can generate new sounds!
The pitch and retriggering rate controls shape its harmonic ratio.
Although the sonic outcome is clearly different from FM, I’m surprised by the versatility of the the system that I came up with.
It litterally allows me to generate new sounds (whose texture and timbre are easy to manage) as well as create odd syncopations.
If the retriggering function is activated while the normal sequence is playing, it sneaks in there some other hits that are free from the main clock source.

 

             CLICK HERE TO DOWNLOAD THE DEMO PATCH

 

 

 

 

MY DISCOVERY

I made some interesting observations while playing with my new creation.
I noticed that tweaking the pitch control while the retriggering rate cycles at a very fast rate, seems to generate a similar effect to Pulse Width on a square wave.
The sound acquires the typical nasal quality of square waves especially with samples that have a pronounced low frequency content.
In various cases, changes in the pitch seem to match changes in the PW of a square wave.
To support my thesis, I observed the signal produced at fast retriggering rate – that I’ll call Signal 1 for convenience – with an oscilloscope and compared it to a square and sawtooth wave.
The oscilloscope showed major similarities. Here is what I observed:
1. Bringing the pitch to a high cycle generates a spike in the waveform. The size of such spike is directly proportional to the increment of the pitch.

                     

 

 

 

 

                         

                                           Pitch = 1.64                                                                                                                        Pitch = 1.71

 

 

                                          Pitch = 1.74                                                                                                                           Pitch = 1.82

The growth of the spike has a strong exponential behavior. As a matter of fact, it increases extensively within a very narrow range of pitch change.

The spike disappears almost completely when the pitch is set to about 1.42.
Although the waveform is clearly not a square, it presents a curious feature typical of square waves. In the second picture I raised the volume to investigate this phenomenon.

          
                              
                                           Pitch = 1.42                                                                                                              Pitch = 1.42; + 17.8 dB
2. On the right is the output of a square wave produced in Ableton with a PW of 100%. Observe the small spikes present at the end of each cycle. Still not satisfied, I routed the signal into a 24 dB/Oct low-pass filter and cranked up the resonance. Once again, the spikes are enhanced, recalling a similar behavior to Signal 1.

   

               
                                       Square Wave (C1)                                                                                                         Square Wave (C1) + Resonance
3. Signal 1 produces the same effect on my ears induced by a square wave and sawtooth. When taking the headphones off, I was left with the same tickling noise that I recall feeling while building the SSO.
I’m still not sure of what is going on here; however, I’m convinced that there is a relationship between the Signal 1 at fast retriggering rate + high pitch and a square wave PW.

Leave a Reply

Your email address will not be published. Required fields are marked *