Hydrogen is a software synthesizer which can be used alone, emulating
a drum machine based on patterns, or via an external MIDI
keyboard/sequencer software.

It features a modular and graphical interface based on QT4, has a
sample-based stereo audio engine, with import of sound samples in PCM
formats. Furthermore, a pattern-based sequencer with the ability to
chain patterns into a song. Up to 64 ticks per pattern with
individual level per event and variable pattern length are possible.
32 instrument tracks with volume, mute, solo, pan capabilities are
provided, and there is multi-layer support for instruments (up to 16
samples for each instrument). Human velocity, human time, pitch and
swing functions are implemented as well.