Since Mile Zero is now the #11 on a Google search for "virtual pedalboard" (much to my dismay when I first started looking into using a laptop for my bass effects rig), and since I've had a few searches for information after first writing about it, I'd like to go into depth about the final results. As I've said, I'm not planning on using the laptop live for a variety of reasons, but it does make a fine recording setup.
As usual, I've worked on doing this on the cheap. There are plenty of ways to spend a lot of money for a laptop effects rig--Native Instruments makes Guitar Rig expressly for that purpose--but for many hobbyists like myself, spending a lot of money on that software seems extravagant, and might not go over well with significant others. I also see it as a personal challenge to do more with less.
I did end up purchasing one piece of software to run the pedalboard: Phrazor, which is technically a synthesizer workstation. Phrazor is built to let keyboardists and sequencer-based musicians easily run complex sets of virtual instruments and effects live, but it also hosts audio-based plugins. That makes it versatile enough to adapt for our purposes.
Phrazor provides 64 "Tracks," which are basically 8-slot effect racks. They can be chained or routed to other tracks, before being sent out through the audio channel. My pedalboard project contains one track for effects and another track for the Mobius looper plugin--the mix from the first track is sent to the second, so that the looper gets the complete effects mix.
Each track contains its own mixer. Click here for a screenshot of the effects track routing. There are two busses through the mixer, A and B. Each plugin receives an identical dry signal from the track's input (which can come from external or internal routing) along the A bus. The B bus is wired in series--it gets signal from a previous plugin, in a chain. So you use the A bus to mix multiple effects simultaneously, while the B bus feeds them into each other.
I realize that's tough to wrap your head around, so let's walk through the screenshot by way of illustration. Three effects--the compressor, Tube Screamer, and the Marshall Amp--feed into the B bus. Those effects are meant to be chained together. So when I activate the fuzz preset, my bass signal feeds first into the compressor. From there, it's sent to all plugins along the B bus, but most of them are muted. The first unmuted plugin is the Fuzz Plus, so I get my low-end distortion from there. At the same time, the signal also passes from the compressor into the Tube Screamer, which is muted but hooked into the signal chain (see the yellow arrow, indicating that its output is sent to the next plugin along bus B). The Tube Screamer sends to the Marshall, also muted and in series, before it finally emerges through the unmuted low-pass Filter. Because the last set of plugins have their A inputs muted, they get only wet signal from the previous plugin, and no dry signal from the main track Input.
By controlling the mixer's muting and signal flow, I can control which effects are heard and which ones are effectively bypassed. For my envelope pedal, for example, I mute everything except the GreenMachine Wah plugin. Phrazor stores the mixer state--along with any saved plugin presets--in the Track states to the lower right. It switches between those Track states in response to MIDI notes, which I trigger from the floor pedal (click here to see a screenshot of the remote states view). Technically, my floor pedal only sends program change messages over MIDI, but I use MIDI-OX to translate those into note messages for this purpose.
So that's effectively how the pedalboard itself works, but it doesn't explain how to record it. I have two audio workstations that came bundled with my recording hardware. The Tascam US-122 audio interface came with Cubase, which normally I prefer. Unfortunately, Cubase won't record post-effects, so I can't use it for this project. Instead, I host the Phrazor pedalboard as a VST inside of Ableton Live Lite, which came with my M-Audio O2 keyboard.
It barely works: Live Lite 5 only supports four tracks, and Phrazor needs three to run the pedalboard. Click here to see a screenshot of Live set up to record. "1 Audio" receives the bass signal from the interface and hosts Phrazor. In order to get MIDI messages to the plugin, we need a second track--"2 MIDI"--that passes input on to the first track. See how "1 Audio" has its Audio To control set to "Sends Only?" That allows it to feed to another track for recording ("4 Audio") instead of going to the Master output. If we recorded on "1 Audio" we would only be getting the dry signal run through the current Phrazor preset. Recording the MIDI signals as well would theoretically play back the control messages with the audio, but it's easier and more reliable to mix the output to an audio track during the song. The last audio track, "3 Audio," records directly from the microphone for vocals.
I've recorded a low-quality .mp3 of myself using the virtual pedalboard so that you can hear the results of all of this. You can click here to hear a walkthough of my effects board, including a breakdown of the elaborate distortion effect I wrote about in this post, and a familiar tune looped to show off how it all works in practice.