Basalt

A bass guitar emulation, from an electric guitar DI.

No bass required. And since the part comes from your actual guitar take, the low end locks tight with the riff, so it is useful even if you already own one. Not pitch-to-MIDI, not a synth: it's your actual performance, an octave down and voiced like the real instrument.

Full version available for purchase at lodestaraudio.com.