ModSynth allows the creation of many kinds of music synthesizers. Connect any number of oscillators, filters, delays and other synthesizer modules in a graphical editor. Then, adjust the settings of each module while playing the instrument to get a desired sound. Save as many instruments or variants of an instrument as you'd like. Eight built-in instruments are provided to help you get started.

The free version contains the following modules:
- Keyboard
- Pad (for theremin-like control)
- Oscillator
- Filter
- Envelope
- Mixer
- Amp
- Sequencer
- Delay (echo)
- Output (with scope to see the sound)

In-app purchase the full version ($4.99 US) to remove ads, expand polyphony (from 3 voices to 10), unlock advanced capabilities, and access additional synthesizer modules:
- Arpeggiator for sequential playing of the notes in a chord
- Melody for more complex sequences of notes
- MultiOsc for strings and other chorus sounds,
- Unison for more complex chorusing,
- Operator for building FM synthesis,
- PCM for sampled sounds (WAV and SF2 SoundFont files),
- Reverb for simulating room acoustics.
- Crusher for adding digital distortion.
- Compressor to combine all voices and even the sound levels
- Pan to direct sound to either left or right stereo channels.
The full version also provides the ability to record sounds to a WAV file.

ModSynth has USB MIDI support for external MIDI keyboards. It has low latency on devices supporting Android low latency (such as Nexus). All oscillators are anti-aliased, providing low distortion at higher frequencies.

A guide to using ModSynth can be found at http://bjowings.weebly.com/modsynth.html.