Using Phase Cancellation to Create Blooming Ambiences
|The red lines represent sends from a guitar track to two send returns. Each has a reverb inserted (in this example, the reverb from Line 6’s POD Farm Elements). One return also has a plug-in that reverses the phase.
WHEN YOU’RE ONSTAGE, reverb sounds different. You initially hear the direct sound from your amp, and then you hear the reverb as it reflects off the surfaces of the acoustic space and back to the stage. This causes the reverb to bloom, where it takes a short amount of time before you hear it at its maximum level.
Many years ago, I wrote a do-it-yourself article for Guitar Player on building a spring-based, analog reverb circuit to emulate this effect. But forget the soldering iron. Now, you can create this luscious, ethereal sound within most recording software. Here’s how:
 Create two Sends from the track to which you want to add reverb. These need identical settings for Send Level, Pan, and Pre/Post.
 Insert a reverb in the Return for one of the Sends, and adjust the reverb controls for the desired reverb effect.
 Insert the same reverb— with the same settings—in the other Send Return (both Send Returns should have identical control settings). If possible, copy/duplicate the first reverb to ensure the settings are identical.
 Reverse the phase (polarity) of one of the reverb Returns. This process varies from one DAW to another. It may be as simple as a software switch, or you may need to insert a phase-switching plug-in such as Sonar’s Channel Tools, Studio One Pro’s Mixtool, or Ableton Live’s Phase.
 When you flip the phase, the reverb effect should disappear. If not, then either the Send controls, reverb parameters, or reverb Return controls differ for the two sends. Find any discrepancies, and fix them before proceeding.
 Now, increase the reverb time on one of the reverbs, and play. Initially, the reverbs will be very similar and will cancel each other out. As the reverb decays, however, the two reverbs will differ more—resulting in less phase cancellation until the reverb tail “blooms.”
Due to the cancellation, you’ll probably need to increase the reverb Return levels to compensate for the somewhat lower overall level. Remember, though, the two reverb Return levels need to remain identical. If your DAW can group faders, then group these two controls so adjusting one adjusts the other.
This effect is particularly effective with languid single-note lines, but it can also sound really evocative with vocals and even drums. Try it!
Craig Anderton has played on or produced more than 20 major label releases, mastered hundreds of tracks, and written dozens of books. Check out some of his latest music at youtube.com/thecraiganderton.