New blown/tongued envelope gen circuit (sax/clar/violn)

[Ricko]

Exploring circuits for further envelopes that are complex to do with conventional ADSR envelope generators: this time for the characteristics of certain blown or bowed instruments.

For single reed instruments like the sax or clarinet, when you play a musical line, you start the line by blowing (the outer envelope) , but you articulate individual notes using your tongue to block the reed (the inner envelopes), while maintaining a constant wind pressure. So the initial note in a line has a different kind of attack (longer) while the internal notes have a much shorter attack.

This envelope generator provides this kind of envelope. It is also found in some bowed instrument playing, too. You use the velocity to get the dynamics of the phrase portion, not just the current note.

So the inputs are a gate signal and a velocity signal (which can be continuous). There are three control pots:

* Inner Attack/Release sets the attack of notes where there has not been much time between the current gate on and the previous gate off. It sets the release of all notes.

* Outer Attack/Decay/Connect sets the attack of notes where there has been a long time since the last note off. (Decreasing the initial attack time also decrease the gap where the inner attack effect operates. It also can effect how quickly a change from loud to soft velocity can occur.)

* Velocity allows softer and louder attacks. High velocity increase both the sustain output but also adds a little ledge at the beginning of the note for a more definite start. (At maximum velocity, the envelope output is limited by a diode clipper, to reduce variation in the level of shorter notes.) [UPDATE: no pot now. Fixed value.]

In the chart below you can see the alternating blown/tongued sections, especially at the start. You would adjust your playing style naturally to make best use of this effect.

If using some sequenced or algorithmic material, you could use a slow LFO to the velocity input to get more interesting dynamics and more musical lines.

UPDATE: The following schematic is superseded by the one later below.

---

SaxEG1.JPG
Description:
Filesize:	208.65 KB
Viewed:	487 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

---

[LFLab]

Interesting circuit, did you build it?
Keen on finding out how it responds to key velocity, could be very interesting.

[Ricko]

I have built this EG now, and made several alterations to the circuit, attached. The EG allows the inner notes to be articulated separately, even though the outer shape keeps a legato line, without requiring a long decay.

(This envelope generate is intended for keyboards and automata, not wind controllers.)

It takes a bit of getting used to playing, but it seems you get the best result by thinking in terms of phrases or lines where how hard and long you play and pause immediately previous notes impacts the next note: so you can get swells and fades as you play, more like wind or string player's articulation, but with very clearly distinct individual notes. UPDATE: Quite fun, being able to play legato lines but with detached notes. What is really unexpected is that by playing a really soft note just after a note at its maximum, you can get a kind of Decay envelope for that note (at the Outer rate).

The shape of the envelope varies with the velocity, not just the level. The effect is that between ppp and m velicity, the change is mainly in level; between m and fff the change is in the front of the note, as the direct gated velocity contributes more than the integrated gated velicity.

(I removed the velocity pot with a fixed value. You can tweak the 1.2M resistor and the 470k mixer resistor if you want louder or softer level at minimum velocity. Three knobs and three pots dont fit into 4HP happily. And maybe the module is easier to learn to play with if it has a dependable velocity response?)

(The chart shows the variation in responses to the velocity input. Usually this will be a gate-like signal of varying height that changes with each note, but continuous signals can also be used and that is what the chart shows.)

(I hope to make an audio example soon)

UPDATE: The output function is roughly

G = 5V if gate > 2_DIODE_DROPS 
GatedVel = G/VEL_STRENGTH + Min(G, Vel) 
Outer = min(G, AttackRelease(GatedVel, slowPot, slowPot+ MIN_RELEASE)) 
Inner = AttackRelease(Outer, fastPot, fastPot) 
Out = (GatedVel/GATED_VEL_ATTENUATE + Inner) * BUFFER_TO_7V_MAX

(I think there is some small feedback effect too, from the output of Inner back to the input of Outer via GatedVel.)

[UPDATE: Use larger e.g. 56n cap on output buffer: just 10n gives a kind of thump on the gate off sometimes.]

---

SAXEG2.JPG
Description:
Filesize:	191.03 KB
Viewed:	355 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

---

[Ricko]

OK, here are two samples of this envelope generator, to demonstrate the various dynamics. No knobs were tweaked, all the dynamics are from the keyboard.

These were done with only about half an hour of familiarization, so I expect more familiarization would allow better, but I think it shows the melodic or lyrical dynamics, where your keyboard velocity is steering the swell or fade of the current and next part of the phrase.

beere.wave has a long trill, to show how the dynamics can swell and fade even when each note is fairly (or randomly) detached. (If you look at the wave in an audio editor, you can really see the dynamics, if your ear is not quite atuned to dyamic phrasing yet.)

Both examples use the same patch with different settings:

KCV -> VCO -> constant width waveshaper (sharkstooth out) -> VCA -> out
LFO -> VCO (vibrato)
Gate -> blown/tongued EG -> VCA and to waveshaper pulse width
Velocity -> blown/tonged EG

The circuit for my constant-width waveshaper is also on Electro-Music DIY forum.

(Keyboard pitch bend playing up, hence the odd sudden transposition.)

---

beere.wav
Description:		Download
Filename:	beere.wav
Filesize:	2.83 MB
Downloaded:	689 Time(s)

---

---

duderanch.wav
Description:		Download
Filename:	duderanch.wav
Filesize:	1.36 MB
Downloaded:	647 Time(s)

---