It sounds like a detuned SAW tooth that decay over time. Check out my 80s Synthwave beat it has a similar sound that I made from serum. If that is the sound you looking for let me know and I will try to show you how I made it.
Hello, I have seen the Synthwave rhythm of the 80s, and let me tell you that it is true that it has a similar sound that I did with serum. you could try to show us how you did it.