It’s not often we have to issue corrections here at SOS, but I need to make a confession. When I reviewed Expert Sleepers’ initial slew of all‑analogue modules not long ago, I was all too happy to make quips about their names — Ivo, Lorelei, Beatrix and Persephone — sounding like they belong in a children’s book, not realising at the time that those names were in fact Andrew ‘Os’ Ostler’s homage to the Cocteau Twins’ classic 1984 album Treasure. With that gap in my music knowledge very much exposed and since filled, we can move on to the next batch of analogue Expert Sleepers modules, which expands the line‑up in several new and exciting directions, while also not being afraid to forge deeper into some areas already explored elsewhere in the range. In this sense, a fully self‑sufficient system is clearly on the cards, but doesn’t seem to be top of the agenda.

Pandora

First up is Pandora; a “band‑pass filter and distortion processor”, though really it does far more than that. It crackles with character and attitude (befitting of its name’s extra‑Cocteau associations), boasting filtering, distortion, VCA‑like behaviour and even a mode to moonlight as a percussion module. Its vactrol‑based Alpha and Beta knobs ostensibly control low‑pass and high‑pass filtering, though both are in fact moving the centre frequency of the broad‑curve band‑pass filter to create something quite different. There’s also gain, feedback and a wet/dry mix — all with their own CV inputs. If there was one module in the series that could be described as multifunctional, I’d say this is it.

Of course, despite being a band‑pass filter with both Alpha and Beta used together, it can perform well in either a low‑pass or high‑pass capacity; though possibly a little more idiosyncratically than you might want if it’s the only filter in your case. It certainly calls to mind synths like the Korg MS‑20, whose drivable low‑ and high‑pass filters account for the lion’s share of its growling, throaty character, something Pandora has in spades. Its gain circuit is driven by a pair of beastly MOSFET transistors, and at gentler settings (with Mix set to full) can be used like a modestly saturated VCA, while at extreme settings can crank things into aggressive distortion.

On top of all this, the Pandora also has a Low/High switch. This significantly lowers the filter’s centre frequency range and in effect turns it into a capably gnarly drum synthesizer. Of course, this is theoretically possible with any filter; but here it’s presented on a platter, and together with the onboard distortion amounts to something of a masterstroke. Send triggers into the input to ping the filter and adjust the feedback, distortion and filter frequency to create a range of percussion sounds that are smooth, crunchy and everything in between. Beautiful.

Cicely

Things get really gnarly on the distortion front with Cicely, an “octave fuzz” based on Roger Mayer’s famously Hendrix‑favoured guitar pedal, the Octavia. While the idea of an octave fuzz sounds like a simple composite effect, in reality the pedal did — and this module does — something much more interesting. A simple wave or pure tone will appear to jump an octave with the effect at fully wet — far from alien for those used to playing with distortion, but more complex audio will take on a more complex kind of metallic sheen, offer strange harmonics and then some. After experimenting with a few sounds and sequences from within my system, I fed my Rickenbacker 360 into the Cicely and found it predictably gritty, weighty and generally excellent‑sounding.

The Cicely has a few added functions to make it worth the trip to Eurorack. Aside from the obvious CV control, it has a handy envelope follower with both positive and inverted responses; particularly useful when putting things like a guitar through the Cicely, since it creates a CV equivalent of your playing to patch elsewhere. There’s a useful Centre control to create asymmetrical clipping, which amounts to something like pulse‑width modulation, and there’s an extra audio input for summing — cramming, I should say — even more harmonics through the circuit. With the Mix control, this can be used to add subtle colour or, if you’d rather, destroy your sounds completely. It’s worth pointing out that the Cicely makes a very good partner for the Pandora, whose unique filter circuit was perfect for smoothing off occasional top‑end harshness or taking some mud out of the low end, or both. I didn’t even hate the result of driving both gain circuits at the same time.

Aloysius & Amelia

Aloysius and Amelia are a brace of envelope generators offering different takes on a four‑stage envelope design. Suffice it to say: while it may be more familiar and feel the most instinctive, more traditional ADSR envelopes are really best suited for manual playing, while variations on this (that might be better suited to sequencing or cycling) usually end up being simplified to ADR or AR envelopes.

Almost identical in their layout and aesthetic, both Aloysius and Amelia can be set to cycle like a complex LFO, both have controls for particular stages’ response curves, and both offer different modes to dictate how — or if — their respective stages respond to incoming gates. It’s also possible to switch between slow, medium and fast time ranges for different stages.

So how do they differ? In a nutshell, Aloysius is an AHDW envelope, while Amelia is an ADBR envelope. Don’t worry, I’ll explain. AHDW stands for attack‑hold‑decay‑wait, which is also known as a trapezoid generator and closely associated with the EMS synths of legend. It’s worth noting that all of these are time values, unlike ADSR where sustain is a level value. Upon receiving a trigger, its attack stage rises to maximum according to the attack time and curve, where it is held for the duration of the hold time. It then decays, according to the decay time and curve, until it reaches 0V again and then waits according to the wait time before retriggering. It’s particularly good for classy, sparse, cycling envelopes with its wait stage, and also great for generating movement with a variety of gate lengths, or conversely for using with triggers of any length in more of a slew‑limiter‑type capacity.

Amelia, on the other hand, is an attack‑decay‑break‑release (ADBR) envelope. The key here is that break represents a level value; namely that of the decay stage, at which point the envelope moves onto the release stage. I found it helpful to think of break almost as a mix control between the decay and release stages. A high break value will mean that the decay stage will only occupy a fraction of the envelope response, and vice versa; meaning that at one pole it essentially renders the Amelia an AD envelope. At the other, AR. It’s very well‑suited to creating Buchla‑esque, plucky but natural‑sounding responses to simple triggers, so is likely to waste no time making best friends with your sequencer.

Otterley

Lastly, and most recently unveiled, is the Otterley. A multi‑LFO module, it offers an impressive five different LFOs along with the ability to ‘spread’ their frequencies to become more and more asynchronous. The first four of these have their speed, polarity and waveform controlled together, while the fifth operates independently of these with its own speed knob. It’s a simple and immensely useful module, switchable between square and sine waves (though these are customisable via a few trim pots on the PCB) and with a wide range of modulation through positive or negative values, or both. It’s also visually quite lovely with its undulating red and blue jacks. I found it incredibly rewarding feeding all of its LFOs to the various CV inputs of one synth voice; instantly creating a holistic, natural and musical‑sounding ebb and flow.

Having finally made the Cocteau Twins connection, it immediately occurred to me that Expert Sleepers have stopped short of the final track on the album, ‘Donimo’. Perhaps there’s something special up Os’s sleeve to conclude the run? Though since he has also made recent mention of further album‑themed series, I also wouldn’t be surprised if this Treasure range is understatedly rounded off with another sleek circuit in elegant 8HP. In any case, if the first batch of analogue modules didn’t demonstrate that by now Andrew Ostler can more or less do whatever he wants, this second one has. There’s nary a dud here, and with these modules’ prices averaging around £175 — not far off pedal‑price — I’ll offer they’re something of a steal.

From £159.

www.expert-sleepers.co.uk