Voltage Modular is described as 'cross-platform, modular synthesizer for Windows and OSX in AU, VST, VST3, and Pro Tools AAX formats that also runs standalone on both platforms'. There are more than 10 alternatives to Voltage Modular for a variety of platforms, including Windows, Mac, Linux, Android and iPhone. The best alternative is VCV Rack, which is both free and Open Source. Other great apps like Voltage Modular are Cabbage Studio (Free, Open Source), miRack (Paid), NimSynth (Free, Open Source) and SoloRack (Freemium).
I wanted to build a music creation tool that is easy to use, accessible and free. Zupiter is a synthesizer and step-sequencer that runs in a browser, meaning you don't even need to download and install any software to use it.
Hexen is a virtual modular Eurorack synthesizer for Android featuring 50+ modules in an accessible, touch-focused interface. All of the internal signal paths in Hexen have 32 bit resolution and are clocked at 48KHz. The final rendered audio is 16 bit 48KH.