While trying to play some very difficult bass line which is much easier to be played on guitar in both,musical and technical sense,i was experimenting with some pitch shifting VST plugins,trying to pitch shift my guitar and use guitar instead of bass.I did not expect to match of that try but i found a plugin chain that works extremely well.In fact it works so good that no-musician can't tell if it is played on guitar or bass.Even bass player can't tell difference on first hearing.

Here it is: you need VST pitch shifter to transpose your guitar 12 semitones down and VST amp simulation.The second part is easy,there is many very good VST amp-fx-cabinets simulators.To mention few of them:Amplitube,Amplitube2,Guitar rig,Aura-pro etc...But first part-pitch shifter, is dificault.No one worked well,even expensive ones.Than I found FREE VST plugin that works great.That plugin even don't have UI but sounds perfect.it is called pvtransp and can be found here:

http://people.bath.ac.uk/masrwd/pvplugs.html

If you want to hear how it sounds listen my heavy cover of Bach famous melody-Badinerie:

Bass part is played on guitar!Hope you will enjoy!