Hydrogen is a simple real-time Drum machine/sequencer. It features a graphical user interface based on Qt, a sample-based audio engine, Jack/ALSA/OSS/PortAudio and Export to disk audio drivers, ALSA MIDI input, ability to import/export XML-based song and drumkit files, 192 ticks per pattern, 16 voices with volume, mute, solo, ADSR, and pan capabilities, and import of samples in wave, au, and aiff format.