Real-time Stem Separation and Remixing with zplane PEEL STEMS Review

One of the advantages of DAWs is the ability to change pitch and speed at will, and easily revert back to the original state. Moreover, all of this can be done in real-time without latency.

This is largely thanks to the 'Elastique algorithm' used in most DAWs. zplane, the developer of this algorithm, has now released PEEL STEMS, which provides stem separation functionality that's garnering a lot of attention in the music production field.

PEEL STEMS is a real-time stem separation plugin that can be useful for sound quality improvement or remixing. It's also simple to operate, making it easy for beginners to use.

This review was conducted with an NFR (Not For Resale) license provided through Plugin Boutique, which is currently running a discount until July 31st. This article is not a sponsored review, and the link does not contain any affiliate codes.

How to Use PEEL STEMS

The usage is very simple. When you load the plugin, you'll see knobs for Drums, Bass, Vocals, and Other at the bottom. As soon as you play the track, the source is divided into drums, bass, vocals, and other instruments.

Here, you can solo just the drums and bass, or mute the vocals. Turning the large knob adjusts the volume of each stem. The 'Isolation Fader' bar below allows for fine-tuning of the separation degree.

The graphic analyzer at the top shows the stereo image on the X-axis (left, center, right) and frequency bands on the Y-axis. When you play the track, you'll see four colors of data moving, corresponding to the colors of the bottom knobs: green for drums, red for bass, yellow for vocals, and blue for other instruments.

This allows you to get an idea of the frequency distribution in the current track. For example, the frequency distribution of the bass, shown in red, will mostly be at the bottom of the screen. If it's mixed in center mono, the red will be distributed in the center of the screen.

You can drag the mouse over this analyzer area to solo just that area. Pressing the 'Invert Output' button lets you hear everything except the dragged area. I'll mention why this feature is useful shortly.

Now, let's look at three ways to utilize PEEL STEMS.

Creating Backing Tracks (MR)

The most common use for stem separation tools is creating backing tracks. Thanks to recent advancements in AI technology, it's now possible to separate or remove vocals at an impressive level.

PEEL STEMS can also turn a regular audio file into a backing track by just muting the Vocals knob. However, it's not as sophisticated as Gaudio or Logic Pro's Stem Splitter. This is because PEEL STEMS operates in 'online (real-time)' mode, unlike the 'offline' mode of the other two products that require some processing time.

Therefore, the quality of vocal separation is somewhat lacking compared to other products. It's better suited for reducing vocal sound to use as a reference guide, rather than creating a completely clean backing track. You can conveniently and instantly reduce or increase vocal volume as needed.

Improving Sound Quality

Often when listening to old recordings, you might encounter issues like vocals being too loud, lack of bass, or flat-sounding drums.

Stem separation tools can be used to adjust volume balance by dividing problematic parts and individually reinforcing them.

Plugins like PEEL STEMS that allow real-time processing make it easy and convenient to improve sound by adjusting instrument volumes while listening.

It's also possible to process specific areas individually by selecting a particular area in the analyzer and routing the rest to another track.

For example, let's select the bass area, which is mostly visible as red below 500Hz. Although this area contains other instruments as well, we aim to emphasize this range to create a solid sound that forms the core of the song.

The method varies slightly depending on the DAW. Using Reaper as an example, as it's the easiest to understand: Connect Send Output 3-4 from the first track with PEEL STEMS to the second track. Output 1-2 plays the dragged area, while Output 3-4 plays the rest.

In other words, only the dragged area (Output 1-2) plays on the first track, while the rest (Output 3-4) plays on the second track.

I added a saturator and compressor to the first track to reinforce the core. On the second track, I added some spatial effects to widen the stereo field.

Unfortunately, this feature can't be implemented through routing in Cubase, Logic, or Studio One. Instead, zplane recommends duplicating the track and using the area Invert function within PEEL STEMS on the second track.

Remixing

You can completely mute specific instruments and sequence in new virtual instruments. Changing drum instruments often gives a different feel. Or you could mute Bass and Other and create a remix with entirely different chord harmonies.

Using this in combination with the sound quality improvement method through routing mentioned above can result in even better quality remixes.

Advantages and Disadvantages of PEEL STEMS

The biggest advantage of this plugin is that it can be used in real-time. It's really convenient to be able to change knob values and apply changes immediately whenever needed. Although there is some latency, it's very short considering the functionality of the plugin.

The downside is the quality, which is noticeably different from 'offline' stem separation tools. It seems that real-time stem separation tools can't yet match offline methods. Nevertheless, the quality is high for a real-time tool, and it's clear that the technology has advanced significantly.

In terms of pricing, considering that Gaudio requires a subscription fee and Logic Pro's Stem Splitter function requires a Mac with an Apple Silicon chip, PEEL STEMS has the advantage of creating an environment conducive to remixing work at a relatively low cost.

In summary, in terms of sound quality, it's still difficult to compare real-time tools like PEEL STEMS with other offline stem separation tools. However, it will enable very fast and convenient work for sound quality improvement or remixing purposes.