SQ8L is a software model of Ensoniq’s classic 1980s synth SQ80. The SQ80 features 3 digital wavetable oscillators for each of its 8 voices which are fed through analog 4-pole lowpass filters (-24dB gain) with resonance. Sound parameters can be modulated by 4 envelopes, 3 LFOs and several MIDI sources. The SQ80 also has a predecessor, the ESQ1, which can do most of the same stuff.
Although the technology may seem obsolete, these synths can produce a wide variety of interesting and extremely usable sounds. Thanks to the lo-fi oscillators and the analog components it can sound very digital and dirty, but also very analog and warm. Which is a good thing because modern synths often tend to sound rather clean.