Seems simple enough, right? Copy the bass track, edit with Melodyne, and drop all those adorable little orange blobs down an octave. So you do that and… well, it just doesn’t sound all that impressive.
The secret to a great octave-divider bass sound is EQ. Insert a Pro EQ in the track you octave-divided with Melodyne, and edit the settings as shown in the screen shot. The goal is to remove most of the high frequencies that have pick and finger noises—we already have enough in the primary bass track, so adding more artifacts just clutters the sound.
The screen shot shows a High Cut setting of about 600 Hz; you can take it down further, but when the frequency reaches about 200 Hz or so it sounds more like a synth sub-bass (not necessarily a bad thing, especially if you add a little limiting).
And that’s really all there is to it. When you bypass the EQ as a reality test, you’ll hear for yourself why EQ is indeed the secret of virtual octave-divider bass.