Theremin as synthesiser controller (2)

I used the last post on this thread (http://www.thereminworld.com/forum.asp?cmd=p&T=4567&F=1&p=3)- So am continuing it here.. But at the moment I have nothing more to say.... ;-)

fredM said:

[i]My ideas about combining MIDI sequence and Theremin CV are more along the lines of having a note sequence whose register was changed, or having a sequence of some kind driving the VCF while tuning was controlled by the Theremin.. I never had any ideas about how one would use this ability really..[/i]

that does sound useful!

-you could create a rhythmic pattern by having the MIDI kick the VCF in some repetitive manner

-you could have the midi kick you up to a particular register at some part of a song (to avoid the super-sensitive high-register 1-2 inch region next to the e-plus antenna), or arpeggiate whatever you happened to be playing, C64 style... i guess that's all assuming the slim phatty really just adds the MIDI determined CV to, say, the CV input coming from the eplus...

[i]" i guess that's all assuming the slim phatty really just adds the MIDI determined CV to, say, the CV input coming from the eplus " - Hewson [/i]

Yes, it does [i]assume the SP really just adds the MIDI determined CV [/i]..

I do not see how it could be otherwise, though.. The basic CV system is pure simplicity - all one ever needs to do to change pitch is to add or subtract a voltage (83.333mV per semitone) and this operation will cause the 1V/octave module to shift its frequency accordingly.

The manual does not give much data on combining CV signals from the MIDI-CV and CV inputs, but the diagram shows independent CV inputs to each block from each.. The only way this could be 'real' and make any sense is if these signas (CV from M->P and CV from external inputs) were summed in each block.

The Arpagiator is not shown in the diagram, and I assume that this is part of the digital system (MIDI Reciever / interpreter) and will appear as appropriate CV's on the MIDI-CV outputs.

I do not actually think there is likely to be any problem combining pitch-related external CV's with pitch-related CV's generated from the MIDI section.. The area I am more unsure about is the volume CV's..

Ideally, one would want the external Volume CV input to modulate any internally generated volume CV signals.. As in, if the external volume CV was '0' then no internal volume CV would get to the modules, but as the external CV increased, it multiplied the internal CV so that, when the external CV was 'MAX' the internal CV was multiplied by 1.

I am sure the above will not happen on the SP - and that volume CV's will be added.. this will (I guess) cause CV 'clipping' in some cases, and will not allow smooth volume control if there is any volume CV data being generated internally..

[b] Edited 17/02/11 -> [/b]
Everything should be fine if the internal volume CV's can be turned off, or turned right down to 0.. One would lose any volume dynamics embedded in the MIDI data though..

The other possible problems relate to the envelope generators.. If these are triggered, their outputs will probably be summed with the external CV driving a block.. Again, these EG signals will probably need to be turned off or turned down.

It will all depend on what one wants to do..

The easiest solution to all the above volume related issues is to have a seperate VCA driven from the Theremin volume CV, and feed the audio from the SP through this..

LOL! - This 'argument' seems to have gone full circle! ;-) Nothing beats a true modular analogue synth !

Fred.

blargh, thx fred, i hadn't thought about the gating at all..!

for what it's worth, re: the $60 korg monotron, people have found out that the "layer of hiss" problem comes from the cheap-o amp that they use on the outbound VCF signal.

(if you're curious, the discussion starts around here) (http://www.muffwiggler.com/forum/viewtopic.php?t=26319&postdays=0&postorder=asc&start=60)

although it involves desoldering an SMD chip (yikes), if it works, you're looking at i guess $90 for a monotron + upgraded amp chip (+ xx hours of hair pulling from soldering these tiny things), which would give you a VCO and VCF, which is not bad at all.

you would still need a VCA to take the volume CV and apply it to everything...

the VCA, by itself, is probably not such an intimidating project from MFOS or mattson mini modular - $82 for a pre-assembled, tested mattson QUAD vca! (link) (http://www.mattsonminimodular.com/shop/index.php?main_page=product_info&cPath=1_2_14&products_id=31)

so that would be a pretty inexpensive solution if the synth hacksors ever figure it out... just take note that relative to other options, you are basically just getting the ability to have a sawtooth or sine wave (via filter)

Ouch! -
Just looked at some of the Monotron discussions and schematics.. Ok, if its $60 one cant be too fussy.. but.. use of LM324 in the audio path (particularly close to VCF), and the VCF design itself - Yuk! Must admit that I have never been a great fan of Korg analogue synths.. Loved some of their digital stuff though (01W-FD was a superb synth workstation IMHO).

No, from what I have just seen, even at $60 this Monotron does not look like a good buy as a Theremin 'expander' - if one was using a Gakken as the controller, perhaps.. But the EW+ needs something of reasonable quality to follow it - using EW+ with Monotron is too close to Sacrilege for my liking! ;-)

Fred.

(ps - from what I can see, the Monotron does not have a true VCA, and its gating topology would probably make it completely unsuitable for use with any theremin, even if it was a pleasent synth)

FredM wrote: [i]from what I can see, the Monotron does not have a true VCA, and its gating topology would probably make it completely unsuitable for use with any theremin, even if it was a pleasent synth)[/i]

this is DEFINITELY true - it is just a simple on-off gating thing which sounds horrible with a theremin. the monotron really is basically a toy, BUT i think that if you add a VCA (driven with the eplus' volume CV) it starts to behave more musically with the theremin and does a reasonable job at spitting out a pure sine-wave like tone, which stays "clean"* down into the bass frequencies unlike the eplus' own signal... since i have a VCA, i'll try to put together a demo - it's just hard to try and point the video cam in all the right places when you're also trying to play a theremin!

*(until the VCF problem is fixed, you would need another EQ or low-pass filter to filter out the layer of hiss on top...)

EDIT: here are a few recordings of the (cv modified) monotron controlled by the etherwave plus (http://soundcloud.com/hewstigator/theremin-monotron)

-h