OXI Instruments Unleashes ACID: 303-Style Squelch in the CORAL 2.0 Update

The OXI CORAL’s new ACID engine is introduced as a 303-style mono synth, aiming squarely at the classic acid sound palette. OXI Instruments positions this as their take on the legendary TB-303, but with a modern twist: a variable-shape virtual analog oscillator that morphs smoothly between saw, square, and pulse waves. The focus is on capturing the essence of that iconic squelch, but with added flexibility for today’s modular setups.

Post-filter distortion is also on board, allowing users to push the sound into grittier territory. The engine is designed to be played monophonically, with the accent and glide behaviours that define acid basslines. As with other OXI Instruments products, the workflow is intended to be fast and hands-on, making it easy to dial in those signature acid tones without menu diving.

The tutorial dives into the core controls that shape the ACID engine’s sound. The Timbre knob lets you sweep the oscillator waveform from saw at the far left, through square in the centre, to a tight pulse at the right. This continuous morphing is a departure from the fixed waves of vintage acid boxes, offering more sonic territory for adventurous patchers.

Distortion is handled by the Harm knob, which sets the amount of post-filter overdrive. This is crucial for dialing in the right amount of bite and aggression, especially when paired with the filter’s resonance. The Morph knob, meanwhile, is dedicated to accent amount—controlling how pronounced those classic acid accents become, both in terms of distortion and filter envelope modulation.

Accents are a defining feature of the acid sound, and the CORAL’s ACID engine gives you several ways to inject them into your sequences. The Morph knob sets the accent amount, but how you trigger accents depends on your control method. With MIDI, any note with a velocity above 100 is treated as accented, while lower velocities remain unaccented. This allows for dynamic, expressive programming straight from your DAW or hardware sequencer.

If you’re working with CV, you can send a gate to the amp input to accent individual steps. Accented notes are played with increased distortion and a more pronounced filter envelope, giving that signature snap and drive. The tutorial also shows that you can use the velocity or modulation outputs from a sequencer to modulate these parameters, opening up further creative possibilities for live tweaking and generative patches.