Helm is a virtual sound synthesizer available as both a standalone application and an LV2, VST, VST3 or AU plugin. This tool certainly comes with a great graphic user interface, which facilitates its use and responds to its workflow. However, it may still take some time to get used to it, which is why its downloadable PDF guide is always welcomed.
Under the hood, Helm hides a quite decent sound synthesis engine. In general, it produces excellent sound quality. In this regard, it comes with various outstanding features that deserve our attention, such 32-voice polyphony, simple arpeggiator and step sequencer. Likewise, it has a potent modulation system that provides real-time visual feedback and supports multiple sources. What is more, the tool lets you apply filters and effects. For instance, it is possible to combine the formant filter with the stutter effect to create awesome sequences. Regrettably, although Helm is good at generating basses, its leads are not so great.
All in all, Helm is definitely one of the best synthesizers out there, and there is something else that makes it a great choice: it is absolutely free. In fact, it is open source, which means you can download and modify its source code freely. Additionally, it has the advantage of being cross-platform as well.