Drone on, Cre8audio West Pest & Moog Mavis.
The fourth video with this pair in eight days, after the first jam, the FM jam and Left To Their Own Devices. A drone drops the sequence and lets the sound hang, so the interest comes from slow changes in timbre rather than from notes. The two synths suit that well: the West Pest shapes its tone with a wavefolder, the Mavis with a Moog ladder filter, and each can modulate the other through the patch bays.
More with each synth on the West Pest and Moog Mavis tags.