Playing back modulation CV from your DAW doesn’t have to include purchasing a special DC-coupled interface or special software.
I will share 4 free Ableton Instrument Racks to help you modulate, trigger and sync your synths as easy as they’d be plugins. All you need is audio outputs and ENV followers.
A few classic synths had a dedicated ENV Follower input in them including the ARP 2600, Buchla, Doepfer and loads of other Eurorack modules by other manufacturers. What an ENV FLW does is detect the peaks of the audio wave and “rides” those audio waves to give you a direct current signal that doesn’t go up and down like audio but rather stays on top of the audio amplitude shape (aka ENV) and could change its voltage slower than 20Hz (aka CV). In our synths, we decided to call it S. Chain rather than simply ENV follower only because we already have the 1st ENV FLW in the main input and we didn’t wanted to avoid confusion. Then we provided a switch to engage the S. Chain ENV CV instead of the main input CV. If the user flick the S. Chain switch, the CV ENV output also changes to that CV and not just routed the VCA.
From the ENV out we can route it to any other CV destination. So unlike compressors that always effects the level of the audio routed to a VCA, we can route that CV to the filter cutoff, harmony shift or any other synth parameter we’d like to inflict that shape of modulation. Now most users I observed tried to play drums or vocals into the S. Chain but what I had in mind is much more flexible than that.
The ideal audio source for any ENV follower?
Every ENV follower has to have a decay speed. That is the speed the voltage signal will fall between the audio wave peaks we detect their amplitude. If you set it too slow, you might get smoother CV to cause the voltage won’t fall much between audio peaks but you will also limit how fast your ENV can close down ie. the decay factor will be your minimum release time. If you set the decay factor too fast you might get faster decay and release times but you will also suffer more harmonic distortion because the resulting CV will fall faster and lower between every audio cycle. The result might be a jugged CV shape that is audibly distorted. However the problem is becoming smaller the higher the frequency of the audio source we play into the ENV FLW. Personally I asked to fix the S. Chain decay factor VERY fast in order to keep maximum flexibility and nowadays we can generate and playback the modulated audio easily.
How high is too high?
Given that information above you may think that 20kHz will be the ideal audio to play into an ENV FLW but I might argue that it better not be too high because if we want to copy the modulated source we want to keep the audio safe from copy generations and codec degradation. 10kHz should stay safe in most digital copy and codec scenarios and if you consider analog mediums a lower frequency of 6kHz-8kHz is better as treble degradation gets worse. Then we can record and play it back from any audio device. To me that is very exciting so I saved a few Ableton presets you can use and even make your own presets very easily in order to perform, record and playback grooving modulations from any audio playback machine.
The next illustration shows you what could be an extreme case. If you are playing a slow sine-wave of 50Hz into the main input’s ENV FLW.
Considering that a 50Hz cycle takes 20ms between adjacent cycles, you will need a pretty slow decay time to smooth it out. The resulting CV is the blue lines, looks very jugged and its heard well as added, even harmonics. Look at the next illustration in which a sinewave is played into the S. Chain, this time at 400Hz and 8000Hz. The harmonic noise is much smaller between wave peaks and almost disappears.
The musical benefits
The benefits of generating your own modulated sine-wave are plenty! You now are no longer limited to a set shape modulation like an LFO or an ENV Generator. You can shape and process your sine-wave just as you want your CV with any combination of ENV, LFO’s and audio dynamics processors like compressors, gates, expanders etc. while not suffering their audio degradation. You can edit precise modulation shapes never heard before, edit a whole track’s modulation on your DAW or sampler. You can then export such “modulation audio tracks” sine-waves to a WAV or MP3 (or analog tape) and play that audio track into your S.-Chain or main input from your phone or mp3 player for a fully automated modulation track that never fails in a live situation (as long as the audio playback doesn’t). You can even listen to those sine-wave files. Just remember to be careful not to play them loud. By listening you can easily understand their groove and figure out what song they belong to. and finally: you can even play them back from analog mediums, taking advantage of their audio side-effects like wow, flutter and even enjoy their none-linear saturation of the loudest parts. While playing modulation back as audio, any changing of the audio speed will also change the modulation speed which is so essential but so missing from today’s synth control. We tweak our ADSR’s and LFO so carefully to fit the track’s groove and if we later change the BPM while the ENV/LFO remains at the same rate, we may lose the sweet spot of the groove. tying the modulation rate to audio makes audio track’s pitch changes stay in perfect groove
The fabulous four Ableton Instrument Rack presets
The first two Ableton Instrument Racks I uploaded for you are very obvious: The Clickor Tr. and the Triggor Tr. They can be used by anyone with an analog sequencer, drum machine or ENV Generator. They do what their name implies. The 1st plays back click sync and the 2nd plays back the same click sample only to trigger ENV Gen.’s or analog drum machines. You don’t need DC-coupled outputs to play back click. You can, of course make those Instrument Racks yourself easily however, I can save you some time with this download and I added some extra performance features from Ableton’s stock plugins. Features like doubling of the sync speed and beat repeat. Nothing too fancy here. The 3rd Instrument Rack is a 440Hz sine-wave sample player to be played into our synths main input (as melody) and has, also, a few extra’s like arpeggiator, glide and a compressor to shape the dynamics in the familiar way. The 4th and last Instrument Rack, the SideChainor, is an 8kHz sinewave sample player that is meant to be played into the S. Chain input (or any other ENV FLW). Its loaded into Ableton’s Simpler instrument to make use of its LFO and ENV Gen. if you need the more traditional shapes but it has two of them so you can fade between the ENV and LFO shapes. Then again, it also has a compressor added to either squeeze the result or pump the groove in the more familiar compressor side-chain tradition.
Wait, why not MIDI?
If you’r wondering why don’t I just use MIDI well, MIDI can’t communicate exact pitch and ENV. Anyone who tried to record MIDI continuous controller (CC) stream can testify that most MIDI interfaces are just too slow to pick up a smooth dynamic CV stream. But now with those two Ableton Instruments, it’s time to find out if such modulation workflow is helping or is it too cumbersome? I also uploaded the actual sine-wave samples for you so now anyone can download those little samples and make their own sine-wave patches with their own native sampler/synth. They are mono 44kHz 16bit files. The 8000Hz frequency was chosen cause it’s the highest frequency a common audio interface can play if you want to include analog mediums. Any signals above 10kHz might start suffering the analog medium treble degradation and the noise is sufficiently low. 8000Hz in digital mediums make sense cause DJ’s might also be interested in quickening the pitch up or down and with the S. Chain sinewave is too high it will go beyond the frequency response and cheaper tapes. Any lower than 4000Hz would be too close to the ripple noise frequencies. Taking into account a safe margin of pitch adjustments for DJ’s. I think 8000Hz answers all the criteria’s above.
Your feedback wanted!
Now it’s experimenting time. Download those utility presets and and start using your audio outs into your own great and ENV followers. Try it for a couple of compositions and let me know how it works for you.
It can be attractive for live instrumentalists looking to modulate their instruments according to a pre-recorded movements, DJ’s (who can play more than 2 audio outputs at a time), who also want to incorporate live synths in their sets but want some modulation to happen automatically and bedroom musicians who are looking to produce electronic music with their DAW and want that CV modulation to their external analog synths. If you think this way of working is viable and it’s worth pursuing, comment here or write some feedback on this workflow to me at email@example.com.