I would expect there is a setting in the synth (check the manual) - but if not use a headphone splitter to duplicate the cv signal.
Are you able (and will the CS15 do this), to ‘sync’ osc 2 on the Yamaha to osc 1? If so, then the A4 triggering Yamaha should by triggering osc 1 on Yamaha, since it’s sync’d or ‘slaved’ (again, if the CS15 lets you), then your detuned osc 1/2 should be heard when A4 Trigs it. As someone mentioned, the early Korg/Roland/Yamaha analogs used the Hz/Oct and S-Trig…it all gets weird with Gate In/Out…so experiment. The Yamaha manual will definitely be more informative than the A4 manual is on this topic, and then there’s been a recent update I have not done yet concerning ALL the config of CV.
Back to the monster…finally am digging A4 but since I use all hardware keys and rack modules and record audio into DAW, I have great anticipation for overbridge.
Use a Y cable from CV A/B and configure both CVA and CVB to to type pitch. I haven’t tried this myself, but it seems logical (I know…).
From the CS15 Manual, Pg 8.-“Tuning of VCO 1 must be made at the VCO 1 Output. The Pitch OF VCO 2 is changed by Detune.”
Pg. 20 of CS15 Manual -“Use of TWO SYSTEMS”…that and whatever it takes to match that on the A4, all set with some experimenting.
Hi Dawid,
I’d be interested to know if you succeeded, as I should be receiving a CS30 soon. And it should also have some mods for CV input of the VCFs, so I would like to do something similar with my A4.
Of course the CS30 has it’s own sequencer but I dont think it has p-locks 
I’m planning to buy the synth when I go to Tokyo this summer. So it will be some time, unfortunately!
Thank you all for your replies! Really helpful.
fwiw, it works with the cs15’s little brother : the CS10.
Hi!! I’m having some issues to connect Analog Keys to Yamaha Cs15 via CV. I have 2 Y cables, from each Cv output to trigger/cv input from the Yamaha…I’ve set it up to Hz/V but stil can’t trigger both oscillators from Yamaha. And I also can listen to AK oscilattor itself…have you got experience with this equipment (or similar, like MS20), connecting them successfully? Am i missing something in the set up?
Thanks!!
Did you set a trig?
also discussed here …
use the search ! 
I’m not sure what do you mean by setting a trig, for sure I’m missing some information…I went to CV configuration pages, set polarity, hz/v, etc…played keys on AK and also tried by entering trig…does it answer your question?
@avantronica I’ve used the search, but the results didn’t help me to solve my issues, still cannot connect them and make them work successfuly
that’s no reason to create an extra thread though, keep it tidy - you’ll actually be bumping the target audience you seek if you develop an existing thread as per the guidelines
Ok, It wasn’t my intention to make it untidy, my apologies.
Besides that, do you know what I am missing configuring the AK? Why do I hear AK oscillator when CV track is selected? Cable Y 1 has to be connected/set up to Trig1/CV1 or it can be Cable 1 Trig1/Trig 2 and Cable 2 CV1/CV2? Thanks!
@Dawid…I know it’s been a long time since you posted this but… were you able to set it up successfully? If so, would you mind telling me how you set it up? configurations, etc? Thanks!
I just successfully set up a Yamaha CS 5 with an Analog Four. Make sure your cv and gate are going to the right places, that was one issue for me; then you just have to tune an octave I went with c4-c5 with the feet at 64. Also the Yamaha, CS 5 at least, takes an S trig I think.
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I am finally able to connect both synths!! As you mentioned, S-Trig…Gate instead of Trig and 5V to make the trig effective. It was in 0 V and despite the pitch was changing (i realized that with the Initial Level of the Yamaha), it wasn’t triggered.
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recently bought an analog keys with one of the intentions being the sequencing of my yamaha cs 5. this is great news. so you had to use an s trig cable if i’m understanding correctly?
Same cable just on the S trig setting. Best of luck!
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beautiful, really didnt want to bother with some oddball soldering job. thanks!
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