Atomic ($39.99) from AlgoMusic (algomusic.net) is unlike any step sequencer you've used in the past. Sound designer Tim Conrardy and software developer Boris K have teamed up to create this tribute to electronic-music pioneer Allen Strange (1943-2008). Atomic features a circular sequencer interface similar to hardware sequencers Future Retro Revolution and Buchla Arbitrary Function Generator. In addition, you get an arpeggiator and a great-sounding subtractive synth to play the sequences and arpeggios you create. Atomic is a VST instrument plug-in, and in hosts that support MIDI routing from plug-ins (most do), you can route the sequencer as well as two LFOs and a step modulator to other hardware and software instruments.
Atomic's outer ring of knobs sets the pitch offset relative to the pitch of the most recently received MIDI note. The middle ring sets Velocity, and the inner ring sets gate time (note duration). You set the sequence length between 2 and 16 steps by clicking on the step numbers, and clicking on a step's LED silences that step. The step rate is set in relation to the tempo, which can be internal or synced to host, and the range is whole notes to 32nd notes. You can also create your own patterns in 32nd-note increments. When the arpeggiator and sequencer are active at the same time, the arpeggiator plays the current sequencer note, but with its own timing, gate, and octave offset. When the sequencer is off, the arpeggiator functions as you would expect.
The synth has two oscillators with standard as well as additive waveforms, and you can phase-modulate either oscillator with the other. A resonant multimode filter and three effects (delay, reverb, and phaser) round out the signal path. The amp and filter have dedicated ADSR envelopes. A modulation matrix lets you apply two LFOs, a suboscillator, a step generator, and a random modulator to a variety of synth parameters. Atomic is very CPU efficient, and you can easily run several instances to create polyrhythmic sequences (see Web Clips 1 and 2).