From heavy metal to pop, the guitar synthesizer is one of the most commonly used additions for any guitar player. It’s what gives rock songs that piercing distortion and the woeful tones to the blues.

Synth One just launched. It’s a new synth app for the iPad, but it’s also a big deal. Why? Because it is free, open-source, and built by volunteer musicians and programmers. Stay with me here. Synth ...