We reviewed zplane’s Peel in SOS April 2021. It’s an interesting plug‑in, capable of performing some very useful audio visualisation duties. In addition, its Focus Mode option allows the user to isolate a specific frequency and left/right portion of the overall audio signal and mute, solo or route it out of the plug‑in for processing with other plug‑ins. Some DAWs make that last option easier than others, but the functionality is possible in any DAW. You might, for example, use it to focus in on just the snare drum within a full mix, and then apply additional reverb to just that drum, leaving the rest of the audio unaltered.
zplane have now released Peel Stems and, like the original, it’s relatively inexpensive, but it takes the Stems concept to a new level. The key new element is a stem separation feature that allows you to divide your audio into four stems: drums, bass, vocals and other. There’s a little latency due to the need for a look‑ahead element in the algorithm, but it’s an insert plug‑in that works on the playback signal, rather than operating offline like most source separation software. Rather wonderfully, the audio within the four stems is colour‑coded in the visualiser display, providing you with a very intuitive insight into the frequency and stereo placement of each element in the overall signal. Frankly, if that’s all you used the plug‑in for, existing Peel users could easily consider it a bargain given the ‘loose change down the back of the sofa’ upgrade price.
For a quick mix rebalance, or ducking out a vocal, it produced very usable results.
In principle, the stem separation element is no different from that found within the likes of iZotope’s RX, Steinberg’s SpectraLayers or Hit’n’Mix’s RipX. It lets you solo or mute individual stems, as well as adjust their relative levels in the overall mix. The key difference, of course, is that it operates in real time: you simply insert an instance of the plug‑in on the required audio channel and, the aforementioned latency aside, Peel Stems then lets you manipulate the four stems as desired. zplane make clear in their documentation that it’s unrealistic to expect this real‑time stem separation to be as cleanly achieved as with the various offline options mentioned above, and having ‘unmixed’ a few example tracks with both SpectraLayers Pro 10 and Peel Stems, I’d agree; SLP10 clearly delivered superior results. But the differences in performance were most notable in busier mixes, while Peel Stems’ real‑time algorithms had an easier time with sparser mixes (a low ‑ key guitar/piano ballad, for example), and for a quick mix rebalance or ducking out a vocal, it produced very usable results.