Way back in 1998, we interviewed Dan Rathbun [Tape Op #10]. One of his techniques for mixing was something he called "Split-Spectrum Compression." Simply put, this is the idea of using a crossover to split an instrument into two or more frequency bands to gain more control over its sound. A bass guitar, for example, can be divided into high, mid, and low bands in order to compress — or apply other effects — to each band separately, before blending together the results using a mixer. This concept blew my mind at the time. These days, multiband compressors are ubiquitous, especially in the digital realm, but the crossover technique allows me to use a different processing chain for each frequency band. I've used variants of this approach to help with my mixing sessions and shared many of them in my Lynda.com video courses.

Along the way, the other aspect of sound I wished to have more control over was transients. When the SPL Transient Designer hardware [Tape Op #21] came around, followed by the UAD?2 software plug-in [#67], I was an immediate adopter. Now, I could control how quickly a source entered and left the mix. Other plug-ins, notably Sonnox Oxford Envolution [#113], have added a higher degree of control to transient vs. tonal information, and I have been using Envolution quite a bit lately to restore energy in poorly recorded drums, and reduce hi-hat bleed and ring in snare mics. But now, the innovative minds at Eventide have introduced their Structural Effects technology via the Physion plug-in. They claim this process "separates a sound into its transient (impact/ unpredictable/jagged) and tonal (sustaining/ stable/smooth) parts more effectively and accurately than previous methods." From what I can tell, this is very true.

Simply put, Physion is a plug-in that can split a mono or stereo track into transient and tonal components, and then process these two elements separately within the plug-in. Processing includes many spatial effects (something Eventide is well known for), as well as EQ and dynamics, with pitch and tremolo effects further available for tonal processing. In my experience, learning how to use Physion took a little bit of work. I tried popping it on some drum tracks during a session, but I didn't quite "get it" out the gate and ended up not using the plug-in. What a mistake. At home, and off the client's clock, I tried out Physion on the same troublesome kick drum and was able to gain the control I had needed over the dynamics of the transient and tonal components.

My approach was to use Physion like I would an external crossover, except for splitting transients instead of frequencies. I duplicated the kick track and applied Physion to both, setting one to solo transients, and the other to solo tone. In this way, I was able to process these two elements of the kick sound separately, using non-Physion plug-ins for EQ and compression — which gave me an even wider control over the dynamically challenged kick drum than if I had relied solely on Physion's built-in effects. This method opens up the thought of what may come next with Eventide's Structural Effects. I would love to see a "simpler" version — one that would split audio into transient and tonal components and send to aux tracks, much like Avid's unheralded Pro Multiband Splitter plug-in does for separating frequencies. Come to think of it, integrating a band-splitter with a transient/tonal–splitter would allow ridiculous control over many sounds!

While messing with the drums, I also learned how to isolate the transient, leave it alone, and pitch just the tonal part. Imagine being able to "tune" toms or snare while mixing. Crazy. Then I tried out Physion on other sources besides drums. On electric guitar and bass, it allowed me to separate the pick attack from the sustained notes — and either create a more driving, percussive tone, or soften the attack and create organ-ish tones from guitar chords. Physion can supremely control the level of electric bass clacks, and conversely add attack to bass recordings that sound too mellow. When I went back to a synth patch I had dealt with in a mix the previous day, I quickly realized I could have easily used Fission to reduce the nasty, distorted attack of the keyboard to fit it into the mix better. Damn — might be time for a quick mix revision.

Are there any downsides to Physion? When pushing sounds extremely hard, yes you can get some artifacts, but this should be expected and was never a problem when I was restoring drums. My personal feeling is the product is being sold more as a "whiz-bang" effects unit, but that part didn't interest me nearly as much as the Structural Effects process itself. There are a lot of presets, some by "name" engineers and producers — such as Suzanne Ciani (see the review of A Life In Waves documentary this issue) — but I found myself using Physion more to control and restore sounds, and the presets either were for specific sources, or other times resulted in crazy, overt sounds.

Am I excited to where this technology will lead? Hell yes. I can't wait to have a "standalone" version of just the Structural Effects splitter for use with other plug-ins and effects — or an advanced version that offers both envelope and frequency division. Controlling how sounds enter and leave the picture is key to getting great mixes, and, as an example, I can imagine new ways to tailor the attack and decay of a kick drum at several different frequencies. I feel like we are in an age where we are seeing the true power of digital audio technology coming into focus, and I think this is a good thing.

Tape Op is a bi-monthly magazine devoted to the art of record making.

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