Like AB-ing your mix, sample layering is nothing new. It's possible in all but the most basic of DAWs but it can raise problems that aren't so straightforward. Phasing, flams and frequency clashes can arise while matching levels and applying processing. It can end up being a convoluted process, but Stacker offers a one-stop, intelligent solution for creating powerful drum sounds.
Stacker has three sample layers, a drum synth layer with a range of oscillator options and two effects auxiliaries. Each sample layer has up to four insert effects, with an EQ, high- and low-pass filter on each. Sample loading is handled with OS X Finder or Windows Explorer. This option is rarely preferred to a dedicated browser interface, since the only way to preview a sample (on a Mac) is the native OS X spacebar Finder function. The included sample library is broken down into types and sub-types such as Kick Knocks, Kick Clicks, Kick Verbs & FX, all designed to help you build the perfect kick drum, from low frequency subs right up to cutting clicks.
Once a sample is loaded, its waveform appears for editing. The usual sample start and end points are available, as well as a loop bracket, but it's the surrounding functions that make the sample editor really useful. Non-destructive normalising is a welcome addition as well as per-sample velocity sensitivity on-off. Unfortunately, though, you can't set a range. The Channels section allows you to flip the stereo image or mono the sound. There are also phase-flipping options for dealing with nasty clashes. On the other side are more stereo functions, including an elliptical EQ—which monos everything below a certain frequency—a slider controlling Width and a Sample Delay fader to introduce some Haas Effect to your sound.
Although you have enough sample slots to cover the usual low, mid and top sections of a full-sounding kick, synthesis is often your friend when it comes to sub. Not only does a single waveform tend to sound cleaner and free of clashing harmonics, it helps you tune the kick to the key of your track. This can go a long way when mixing your drums later down the line. Stacker's drum synth is more basic than the one in Maschine for example, but does the job well. You've a choice of saw, square and sine waves (or anywhere between the three), as well as parameters for filtering, drive, click, tuning and noise. It sounds good but it's definitely a functional layering tool rather than a powerful standalone drum synth.
Click any of the sample or synth slots twice and you'll arrive at the insert effects page where four effects can transform the sound. Digitise gives you anything from extreme bitcrushing to vintage sampler emulation while Clip Filter offers subtle to extreme filtering via a powerful Drive knob and multiple distortion types. Mod Shift allows you to choose between a frequency shifter or ring modulator and both can be locked to a chromatic note for extra tuning capabilities. So far, Stacker doesn't offer much more than any standard drum software but it comes into its own at the base of the GUI.
The bottom third of Stacker's interface offers four assignable modulation envelopes with up to eight destinations, a unique Scatter function, a Global pane for easy access to important functions and pitch and amp envelope shapers. While four modulation envelopes might seem like overkill for a sound that lasts an average of two seconds, it makes creative sound design possible. For instance, you can draw a flange effect into the attack envelope or increase the Digitize effect mix as the sound fades away, emulating the behaviour of old sample-based drum machines.
There are plenty of preset modulation envelopes to play with or, if you're feeling lucky, you can hit the Randomise button and experiment with the results. The mod matrix allows you to assign an envelope, macro, velocity, pitch bend or random value to any sample or synth's parameters, and the auxiliary delay and reverb. While the envelopes are more likely to be worked harder on claps, snares and effects, they are useful for adding character to almost anything. As the nature of layering means the sub and lows are controlled by another source, you can get a bit more creative on the mids and highs of your sound without worrying about the fundamentals being ruined.
Scatter is one of the highlights of Stacker. Adjusting the starting time of each layer allows you to stagger the onset of each sound, from just two or three milliseconds all the way up to one second. You can also sync and snap the grid for time-based adjustments based on the project BPM. Sample Magic don't explain how they do it, but something they call "intelligent time displacement" makes for very little phasing, even with the smallest of changes. I assume there's a zero-crossing point sample snap going on in the background, but either way it's a welcome change from the incremental dragging of samples in your DAW timeline.
Stacker is well thought out, but there are some odd omissions. There's no panning in its mixer or bus-specific effects and any MIDI input triggers all four sounds, meaning you'll need a new instance of the plug-in for every kick, snare, clap or hat. Then again, Stacker is £60 and comes with a lot of high-quality samples. It won't replace your go-to drum software, but it's a powerful addition to your percussion production suite.
Ease of use: 4.0