Zipper-like Sound at Beginning and Ending of Synth Sounds in Cloches and Intergalactic

[Dirtgrain]

I'm digging these synth sounds. They are like zippers, croaky sounds or exponential rhythm kind of sounds at the beginning or end of synth sounds in the songs below. I would love some insights on how to make them.

In the first one, I wonder if it relates to pitch drop and how you can hear individual oscillations at lower frequencies. Anything else account for it? Filtering of some sort? FM?

Worakls - Cloches at 2:33 and on
https://youtu.be/VR4eXiuFgBQ?t=153

Slam Duck - Intergalactic at 0:08 and throughout (more at 1:18, 3:18)
https://youtu.be/ldFBwxJ87us?t=6

Many thanks for any ideas.

[Dirtgrain]

Ok, I'm an idiot. I got something like the Cloches sound with Zebra saw in lower notes and pitch shift down. Still more to it. Any ideas are welcome.

[cron]

I can't test this at the moment, but the missing ingredient might be some kind of phase dispersion? The clicks you get when pitching a saw/square oscillator down to subsonic levels would usually be instantaneous clicks, whereas these sound a little more spread out in time. Kilohearts Disperser is the only plug dedicated to this I'm aware of, but in the absence of that you could try a phaser that lets you set the modulation rate to 0 Hz such as the one in Serum's FX rack, convolution with a cabinet impulse which should mess with phases a bit, or the low tech method if you're an Ableton user whereby you stack 7 or 8 EQ Three instances in series without touching the parameters at all (ensuring 'flat response' is checked in the right click menu on each instance).

[Dirtgrain]

Thanks. I almost bought Disperser on sale, but I didn't--and now I wish I had. Will keep it on my list. Time to go old school

[e-crooner]

Maybe it is a monophonic sound so that you can slide your finger up and down the keyboard, like this:
https://app.box.com/s/eok30e268fq8xg9gtpulxl2jg3kxmbo0

[SiloCybin]

you can achieve that by using an envelope to control volume and set to loop. with a short/instant attack. the decay should ramp down right after the attack. if you increase and decrease the decay time as the sound is playing you'll get the "zipper" effect you are talking about.

[Dirtgrain]

Thank you--that's a nice way to set it up.