Centaurus ($7.49) is the first in a planned series of low-cost synths and effects from Koblo (koblo.com), developer of the free, open-source sequencing environment Koblo Studio. This analog-style synth comes in VST, AU, and standalone formats and requires online authorization. (You can try it out in demo mode, which emits occasional noise bursts.) Centaurus presents a compact graphical user interface that has clearly labeled knobs and buttons but no digital readouts. Its built-in preset browser gives you easy access to more than 100 factory presets that are organized as basses, leads, pads, and effects. And, of course, you can add your own.
You get two oscillators with standard waveforms: saw, square, triangle, and sine. Osc 2 has variable pulse width, and, in the only deviation from the analog paradigm, you can route it to frequency-modulate Osc 1. You can turn off keyboard tracking for either oscillator, which is useful for clangorous FM effects, as illustrated by the factory preset Nice Bell Lead. The oscillators are mixed and sent to a multimode (lowpass and highpass) resonant filter that has handy buttons to toggle Velocity and Mod Wheel tracking. The output level is controlled by a dedicated ADSR envelope, and you can route an additional, looping AR envelope to FM amount, filter cutoff, pitch, LFO rate, and pan. The tempo-syncable, delayed-onset LFO has a variety of waveforms, including random, and you can route it to amplitude, filter cutoff, pulse width, and pitch. One-click MIDI Learn rounds out Centaurus's feature set.
Although Centaurus is capable of producing the full spectrum of analog-synth sounds, it excels at ambient washes and special effects (see Web Clip 1). It's simple to program, and the ease of setting up MIDI control makes it a hands-on synth. And the price is hard to beat.