With the simple task of producing LFOs and envelopes — at least, at its most basic level — the humble function generator is an oft‑overlooked but key part of any modular system. While generally considered part of the (less fun, if we’re honest) ‘utility’ family of modules, alongside things like VCAs or mults, many developers are, you might say, pushing the envelope (sorry) with their function generator designs to produce some very interesting circuits.
Of course, modular is an expensive craft: one might save with anticipation to buy an exciting sampler or drum module, but it’s generally with reluctance that we invest in utility modules, despite the fact that they’re essential for those other modules in our system to work at their best. Not all function generators need to break the bank, though.
Here are some of our favourite function generators that will capably augment your patches, all weighing in at well under £200.
ALM/Busy Circuits Pip Slope (Rev II)
British developer ALM/Busy Circuits’ Pip Slope fits an impressive amount of enveloping goodness into a miniature 4HP. Building on the original Pip Slope, its CV‑controllable attack and decay times boast a whopping range, from 1ms to 7 minutes, and it also has the ability to morph smoothly between exponential, linear and logarithmic slopes via a Shape knob. Perhaps most interestingly, it also features a Loop mode that can cycle the envelope with decreasing amplitude or decreasing time if desired, opening the door for delay‑type effects or sweeping dynamic movement across a patch. Barely touching the £100 mark, this is certainly bang for your buck.
Endorphin.es Airstreamer 4
We love Endorphin.es’ aesthetic — somehow they even manage to make a function generator look cool. Condensing the previously 6HP Airstreamer into a Pip Slope‑rivalling 4HP, the Airstreamer 4 selectively offers CV control over its decay time, though not its attack time. This might sound limiting, but there’s masses here: dual envelope CV outputs offer unipolar or bipolar voltage ranges, while a polariser knob can attenuate or invert its output voltage, also providing an additional VCA input to scale and invert the envelope for a “compact side‑chain envelope solution”, in Endorphin.es’ words. There’s even a very smart Volt‑per‑octave input for tuned control when oscillating at audio rates.
After Later Audio Tilt
After Later Audio’s take on a five‑decade old Serge classic, the Slope Generator, the Tilt is described by its developer as “really a jack of all trades.” Like its predecessor, it offers both unipolar and bipolar outputs, adding separate controls for exponential and logarithmic responses at both the rise and fall stage, as well as a gate/sustain function for a full ADSR envelope. Usefully, there are both inputs and outputs for both the rise and fall stages of the envelope, as well as one for both. All the key functions you’d hope for are here, including things like the capacity to use the In input to create a slew limiter, and in a rather lovely black and gold finish, too.
Erica Synths mki x es.EDU EG
The cheapest on our list at just €55, this envelope generator was brought forth by the excellent mki x es.EDU, a collaboration between Erica Synths and educational electronics whizz Moritz Klein, and it seeks to coax even the most timid prospective DIY‑er into the world of electronics and circuit design. Described as a “slightly optimised” ADSR envelope generator, the EG is a simple and useful function generator, configurable to either an ASR or an AD response that ignores input gate time. A toggle switch for looping and an inverted output cap off an interface that’s all about the essentials. A simple kit at a great price, resulting in a great module. What’s not to love? Best order that soldering iron.
Make Noise FUNCTION
Derived from one of Eurorack’s most successful function generators — make that one of the most successful modules — the Make Noise Maths, the Function’s staggering time range begins at 2ms and extends to a possible 25 minutes per cycle, for those truly slow‑growing sound experiments. Beyond this is a flexible palette of linear, logarithmic and exponential functions, as well as inversion and integration for lag, slew and the like. A Hang input allows the circuit, as Make Noise put it, to “stop dead in its tracks” for capable sample and hold, track and hold, stepped movement and more.