MousePlugins X-Or is a free monophonic synthesizer designed specifically for basslines, sub layers and pedal-bass sounds.

Instead of trying to become another huge do-everything synth, X-Or keeps the architecture deliberately focused: two saw oscillators, a resonant low-pass filter, dedicated filter movement and a simple amplitude envelope.

The result is a fast instrument for producers who need solid low-end without spending twenty minutes navigating modulation pages.

Two Saw Oscillators Built for Bass

X-Or uses two continuously running sawtooth oscillators.

Oscillator B can be shifted by semitones and fine-tuned in cents, allowing producers to create octave layers, fifths or subtle detuned beating.

A dedicated Mix control blends the two oscillators before they enter the filter.

Resonant Low-Pass Filter

The oscillators feed a resonant low-pass filter with a cutoff range designed to work particularly well for low-frequency material.

A separate attack-decay contour envelope can open the filter every time a note is triggered.

Short decay settings create tight plucky basses, while stronger resonance can push X-Or toward more aggressive acid-style tones.

Designed to Play Low

X-Or automatically transposes incoming MIDI down one octave by default.

This pedal-bass voicing means a comfortable MIDI part played around the middle of the keyboard immediately lands in a deeper bass register.

The synth is monophonic with last-note priority, making it particularly well suited to bass parts and single-note sequences.

Smooth Glide and Legato

The Glide section provides portamento between overlapping MIDI notes, with times ranging up to 2000 ms.

X-Or also uses soft envelope retriggering. New notes can continue from the current envelope level rather than abruptly restarting from zero, helping prevent clicks during legato passages.

Built-In Waveform and Spectrum Display

The large display at the top of X-Or can switch between waveform and spectrum views.

This gives producers immediate visual feedback while adjusting oscillator tuning, resonance and filter movement.

Output meters are also integrated directly into the interface.

Free With No Activation

MousePlugins distributes X-Or completely free of charge.

There is no license key, account, activation process, subscription or internet connection required.

The developer also explicitly allows X-Or to be used in commercial productions.

Is X-Or Worth Downloading?

Yes, particularly if you want a dedicated bass instrument rather than another large general-purpose synthesizer.

The combination of dual saw oscillators, resonant filtering, contour modulation and glide covers a surprising amount of bass territory while keeping the workflow extremely simple.

For House, Techno, Electro and other electronic styles, X-Or is a useful free instrument that does one job and stays focused on it.