Review: Spectdrum by HD Instruments

Not every plugin is fun and creative, and that’s okay. Some plugins are strictly functional, practical, or informative and serve important roles in the music production process. But I like the fun and creative ones most.

Among fun and creative plugins, many feel like long buffets stuffed with oodles of related options. Thirty modules in a multi-effect sound-scrambling smorgasbord, for instance, or sixty-three flavours of delay, like tasty scoops of ice cream to melt and ooze around your audio.

Then there are plugins like Spectdrum by HD Instruments. Rather than an array of related effects, Spectdrum expands the menu with a variety of tasty concepts. A step sequencer is fun and creative, right? Band splitters, too. Multi-band EQs with per-band effects? Fun, and also creative. Multiple freehand-drawable envelopes? Ditto. Pattern chaining, multi-level randomisation, and using any audio source as input? Check, and check.

But is the creative fun in Spectdrum more delicious than the sum of its parts? Does this tasting menu of individually delectable delights satisfy like a potluck full of filters and phasers? And what, precisely, does it do? Strap on a napkin and let’s dig in to find out.

The (Un)Usual Drum-Spects

Fundamentally, Spectdrum is a four-band gate sequencer. Incoming audio is split into four filtered bands based on the positions of the four colour-coordinated peaks in Spectdrum’s combination spectrum analyser and equalizer.

Each band has its own step sequencer, customisable envelopes, and delay and reverb sends. After seasoning each separately, the four bands are gently folded back together, mixed with dry signal to taste, drizzled with the send outputs, and finished with love (and perhaps a sprig of parsley) from the master effects section. It’s a bit of a mouthful, but the workflow is actually quite intuitive.

So much so, in fact, that I tried my favourite trick with a new creative plugin: go completely off the rails straight away. Some people testing a band-splitting sequencer might lean toward a “robust” input as a first pass — a sustained multi-octave pad, perhaps, or better yet, white noise.

The thing is, I knew those sorts of inputs would work. Partly because it just makes sense to feed a band splitter “rich” material to split. But mostly because I’d already watched the excellent Spectdrum walkthrough video by developer Hagai Davidoff, where he used just those kinds of input sounds (among others) to great effect.

So I went a bit mental. I began my Spectdrum testing with a subtle low drone. I threw a braam at it, then movie dialogue, then a didgeridoo loop. Animal roars, tonal whooshes, sitar plucks, you name it. Some worked better than others – and some made me try different approaches to coax out interesting sounds and patterns.

But I got something inspiring, or at least intriguing, from every single input, no matter how oddball or seemingly ill-fitting. That’s a testament to Spectdrum’s flexibility and made me want to explore even further. But let’s start with the basics.

Great Drum-Spectations

As a sequencer, Spectdrum makes no sound on its own. It must be added as an effect on a track with an audio clip or instrument, or otherwise have audio routed in. Once set up, Spectdrum looks something like this:

Let’s start with the spectrum analyser at centre, which displays the output and optionally input audio profiles when audio is playing. Dragging a coloured dot around the grid alters the Freq(uency) and Gain corresponding to the band (Sub, Low-Mid, High-Mid, or Air) that dot represents in the section below. Band Frequency and Gain can also, along with Q (or width), be adjusted via dials in the band parameters section.

Pressing the Learn button in the analyser allows Spectdrum to detect the strongest audio peaks and set defaults for each band accordingly. As the user manual suggests, the plugin by default treats bands as specific drum types: “the lows pulse like a kick, the mids snap like a snare…”. You can alter this behaviour by manually adjusting the band parameters and each band’s Length for each hit.

These “hits” are specified in Spectdrum’s step sequencer near the top, with four colour-coded lanes corresponding to the bands below. Each band control section has a separate Steps indicator; these range from one to thirty-two steps and can be set independently to explore complex and polyrhythm patterns. Individual sequencer steps can be toggled with a click and dragged up or down to set velocity. Global sequencer options including Step Value, Pattern Shift, and Swing are in a bar above the sequencer lanes.

Spectdrum supports up to eight different sequencer patterns, assigned to the eight slots at upper right. Click a slot to edit a new pattern from scratch or drag and drop an existing pattern into a new slot for a head start. Each pattern slot can be triggered by a MIDI note; the defaults are C0 through G0, but MIDI learn is available (as with most Spectdrum parameters) via a right-click menu, if you prefer personalised mappings.

Below the pattern slots are controls for Spectdrum’s reverb and delay send effects. Delay Time and reverb Predelay can be synced to tempo, with several presets available and individual controls including FB (feedback), Tone, Wobble, and Pitch for delay and Size, Lowcut and Highcut filter cutoffs, Width, and Pitch for reverb.

Each of the four audio bands has Dly (delay) and Rev(erb) send level controls, with one caveat: the delay includes a Reverb level control of its own. At any non-zero value, this pushes the delay signal through the reverb and disables the individual band reverb sends.

Each Spectdrum band also includes customisable envelopes for volume, filter, pan, and pitch. Click to add nodes, right-click to remove, and drag nodes or lines to sculpt the signal. The pitch envelopes also include a control to specify the allowed pitch range.

They’re Drums… and They’re Spect-acular

This seems an apt time to mention Spectdrum’s particularly clever randomisation features. You’ll find die icons in the sequencer, in each band and send effect section, and at top left among the global controls. As with many plugins, you can click to randomise a section’s parameters (or all parameters, with the top left icon), but Spectdrum provides a nifty level of additional control.

Drag a die up or down to scroll between one and six, with the number indicating the relative outlandishness of the ensuing jumbling. Values one through three introduce more aggressive randomisation (or greater density in the step sequencer), with the intensity further rising at values four through six. But past “three”, a few safeguards to preserve tonality (like resetting bands’ Pitch envelopes to default rather than randomising) come off. So be aware that higher-value dice may bite a bit harder.

If things get too wild and woolly, Spectdrum provides Undo and Redo controls at top left, just below the preset selector. Speaking of which, the plugin currently ships with around thirty presets, which do a good job of showcasing the breadth and versatility of potential applications.

That leaves just a few important interface bits, like the icon at top right to save separate learned-MIDI maps (very handy for different styles of project), the sanity-restoring Reset icons in various sections to dismiss runaway experiments, and a bar of global effect controls at bottom. The latter includes a dark/light mode toggle, Lo and Hi filter cutoffs, multi-mode distortion, equalizer, a Smooth de-clicker, maximiser, dry/wet Mix, Wet signal boost, and a Master Out gain control.

Putting It All in Drum-Spective

Working with Spectdrum is intuitive, iterative, and often surprising. The freehand configuration of bands, multiple envelope types, and (to a degree) sequencer rhythms encourage constant experimentation. The results are not always drum-like, but also usable as bass lines, pulses, pads, risers, whooshes, and more. And the mostly-nice to fully-naughty randomisation modes send you just as far down a sound design rabbit hole as you choose to go.

I find Spectdrum compelling, creative, and yes, enormously fun, for two main reasons. The first is that the plugin provides multiple paths to drastically – but also musically (if you prefer) – change the nature of the output sound.

Have a pattern you like, but the timbre doesn’t fit? Swap the input with literally any sample or audio source. Love the sound, but want to morph drum hits into something more melodic? Per-band length, sends, and pitch and filter envelopes can help you get there. Out of ideas for the low-mid range or a third sequence pattern? Surgically randomize until you hear an idea you can build from.

Second, while Spectdrum has many moving parts and features, it doesn’t attempt to do everything you might think of. Nor should it — but it does (mostly) leave room for you to fill in the gaps.

For instance, there is no pre-sequencer audio processing step. If you want to shape the Spectdrum input before splitting, you’re free to use your favourite compressor, fuzzer, exciter, or mangler to do so. Spectdrum stays out of the way — and doesn’t use valuable interface real estate for pre-processing effect controls, trying to anticipate all the various tweaks you could possibly try.

That’s also true for the re-summed signal. A few basic global effects are provided for convenience, but that’s not the heart of Spectdrum and the effects aren’t meant to be comprehensive. It’s not currently possible to apply external effects to individual bands, but assigning each band to separate output channels is included in an update releasing soon, which will open all manner of interesting possibilities.

Beyond the separate outputs, there are only a couple of quirks and feature improvements that seem worth mentioning. First, I found the Undo and Redo behaviour quirky at times; sometimes Undo would remove multiple adjustments, and Redo wouldn’t necessarily restore the last-Undone change(s).

Also, the drawable envelopes are fantastic, but a bit small to work with. The plugin itself resizes nicely, but the envelopes are small windows within. Perhaps a method to expand an envelope while drawing would provide finer control. Along similar lines, the step sequencer is plenty large enough to work with. But I’d love to have additional modes or controls like per-step probability, gate, and other characteristics, which might require multiple sequencer tabs or an expandable sequencer view.

(That update-in-the-works I mentioned is also planned to include new per-step capabilities, generative patterns, sequencer bypass, and per-pattern pitch shifting. Keep an eye out!)

Basically, now I’m just thinking about the enormous possibilities Spectdrum already offers and imagining a couple more. That’s a fantastic indication of a plugin that really resonates with the way I work and encourages me to brainstorm more ways to use it.

In other words, Spectdrum is creative, fun, and there’s plenty more of it left to explore. I hope you saved room for dessert.

Learn more about Spectdrum at the HD Instruments website.