Midicake have reinvented the arpeggiator.

As the first product of Bristol company Midicake, Arp is somewhat specialised — you might even say idiosyncratic. It’s billed as a four‑way arpeggio generator designed to control multiple MIDI layers and produce patterns that are neither boring nor random. Without further ado, let’s arpeggiate!

(Cake)Walk Through

Housed in a compact aluminium box (available in either black or white), Arp is covered in squishy rubber buttons and has a small but serviceable colour display. Its patterns are generated from notes made available from either the eight chord buttons or from an external MIDI controller, with a single octave keyboard provided for quick transposition and for programming the chords, which are initially set to major, minor, etc.

Although I’ll stick with the term ‘chord’ throughout the review, it’s helpful if you don’t think of regular chords but, rather, of a pool of notes Arp can draw from. This pool can be any combination of the 12 notes of Western music and encompasses scales, modes or any grouping of your own — all relative to a root note. Incidentally, a long list of chords and scales are provided, with scales written in upper case so you can easily differentiate between a C min triad and a C MINOR scale.

There are 16 banks of 12 patches in which to store your work and all arrive populated with useful and instructive examples. Once you set each generator’s MIDI channel you can begin working your way though the many parameters, copying patches to other locations as you go to create variations. Saving is done automatically, so operation is both fast and fluid.

Arp weighs 1.2kg and features 5‑pin MIDI I/O, plus a 5V Type‑B USB connection handling MIDI and supplying power. USB and MIDI cables are provided but, when working computer‑free, you’ll need to source a suitable USB adaptor plug. A USB Type‑A host is also present and suitable for controllers such as the Arturia KeyStep, which it can also power.

As the company name suggests, Arp talks MIDI only. It’s therefore a willing partner for hardware synths, VSTs or a combination of both, although the 5‑pin and USB MIDI ports are not separately addressable. Unusually, each of the four generators may be assigned to any MIDI channel and configured for Arp, Chord, Drone or Pad modes on a per‑patch basis.

Pressing the Set button turns the note and chord buttons from green to blue, indicating you’ve entered the menu system. Menu pages are labelled on the panel and where a page has several entries, the display shows the current location. Getting around involves repeatedly pressing the button or combining it with the Up or Down buttons to go back and forwards. Parameter adjustments are made via the tempo encoder, with single increments more easily achieved with the Up/Down buttons.

Four assignable encoders that operate globally provide a direct connection to your favourite parameters without a need to enter the menu system. Call me greedy but it would have been fabulous if these had been assignable on a per‑bank basis — and even better if they could have sent MIDI CCs.

When in Play mode, the display reports the active chord, bank and patch number as well as the octave selected for the button keyboard. However, much of the display is hogged by the tempo, which I didn’t find terribly useful, particularly when externally sync’ed. Arp’s insistence on flashing up the bpm became quite intrusive when tweaking the four macros and left me with weird flashbacks to my tempo‑obsessed Roland SP‑404 MkII.

The four generators are driven by a single start or stop action but each may be individually muted should you wish to thin out some of the mayhem. In addition, Follow buttons instruct the generators to play after the previous one, so if all Follows are active, the four will run in series. Right now, this process permits just one bar of each generator to play before it moves on, which, as we’ll see, is rarely enough to allow an arpeggio to show its full glory.

Arpin’ On

Given Arp’s single MIDI output, you’ll appreciate synths featuring hardware MIDI thrus. For others it’s time to reach for a thru box. When you load a new patch during playback, it kicks in at the end of the bar, although if you send MIDI Program Changes from a sequencer or master keyboard, the patch loads immediately. There’s no way to send Program Changes from Arp to your connected synths so you’ll have to keep manual notes of any favourite combinations of Arp and synth patches — or leave it to your main sequencer or DAW.

We’ll quickly run through some of the parameters available to get an idea why Arp’s patterns are often unlike those produced by a typical arpeggiator. The patterns consist exclusively of MIDI notes, therefore the best results are obtained using instruments that respond to velocity.

Buttons labelled 1‑4 select each generator for editing and a double‑click allows relative changes to be made to all four simultaneously. There are two primary modes of operation — Arp and Chord, the latter offering two subsidiary modes (Pad and Drone). As you’d expect, arpeggios are notes of a chord played sequentially, while chords are multiple notes played at the same time. No restrictions are imposed here — a patch can consist of four chords, four arpeggios or any combination that takes your fancy.

Working through note menu buttons, you first pick a base velocity and gate length, the latter maxing out at 32 bars — ideal when programming very slow patterns. Next, you encounter the various ways of confining and limiting notes, such as locking them to a particular octave or ensuring they never stray too far from the root of the chord. You can force a generator to pick notes from a specific scale or even lock it to a single note, ignoring the input completely. This is handy for percussion or sample triggering.

Note offsets are a simple but effective way of finding parallel phrases within the current chord but for more avant garde experiments, you can bypass the chord completely by engaging Chromatic mode. This is actually a great way to quickly hear what some of the more obscure note‑related parameters are doing.

Time Division is an important menu because it determines the arpeggio speed — from 32 bars per note to 32 notes per bar, with triplets thrown in at either end of the scale! Slow progressions can be a real bonus, say for tossing an occasional extra note into a shorter, more regular pattern. It was while in this menu that I noticed all parameter changes become active immediately when scrolling — there’s no confirmation or ‘enter’ involved. That should certainly keep you on your toes during a live performance!

If Arp were a traditional arpeggiator, the number of notes held down would determine the length of the phrase. Here the Steps parameter does the same, its range from 1‑16 notes. The value translates to how many steps through a chord each arpeggio should travel, so supposing the direction is upwards, a Cm triad (C, Eb and G) with a Steps value of 1 will play only C. A value of 2 will play C and Eb, 3 C, Eb and G, and so on.

In terms of playback direction, the expected Up, Down, Up&Down and so on are supported but you won’t find random because Midicake are philosophically opposed to the concept. Arp’s name comes from ‘Automate, Repeat, Play’ and a firm belief that complexity should always be repeatable. Providing you’re not like me and constantly tweaking every parameter, Arp will therefore always produce the same output from a given input.

Rather less philosophically challenging, the Delay parameter is a timing offset, much appreciated when several arpeggios are layered. If you have two generators set to the same MIDI channel, the action of delaying one and giving it a lower velocity can lead to all manner of juicy MIDI delay effects.

Another key pair of parameters, Bounce and Jump, control the order that notes are selected from the pool and the intervals between them. Starting with nine default or 20 custom Bounce patterns, you’ll be bouncing and jumping around producing sequencer‑like phrases in no time. Lastly, Repeat is the number of times each note plays before moving on.

The next set of menus act upon the phrase as a whole. First up is Rhythm — a rhythmic template applicable to any arpeggio. With a maximum length of 16 steps, it’s a vital tool for adding rests, ties and accents and generally breaking up all that relentless upping and downing. Sixteen editable rhythm patterns are available globally and, I found, are very quickly used up. In a similar vein, Groove’s 16 patterns (also editable) create offsets in time; they serve up everything from conventional swing to more irregular, stumbling feels.

Moving swiftly on, there are three ways to modulate other parameters and bring your arpeggios to life. The first of these, FX, has 127 pseudo‑random seeds and is easily the most ‘out there’ modulation source provided. FX can be applied to introduce sudden shifts in parameters such as Time Division, Step Offset, Delay, etc, and while you can’t edit the patterns, tinkering with modulation amount and the reset frequency can provide some satisfyingly wacky and irregular changes.

In contrast, Mod A and B are simple LFOs with regular waveshapes and frequencies defined in (pre‑selected) multiples of bars up to 32. I’d have preferred them clocked in fractions of bars or able to run unsynchronised but, even restricted as they are, their contribution is significant. The LFOs cover a much wider range of destinations than are available to FX. Indeed, pretty much every parameter is up for grabs, including MIDI channel, FX amount and Rhythm and Groove lengths and direction. Once I tried slowly sweeping the MIDI channel, causing the notes to cascade through all 16 parts of a Proteus 2000 module, I was totally hooked. It’s an arpeggiator, Jim, but not as we know it!

Chained Melodies

One of the sweetest Arp features is actually far from obvious, but if you press the main encoder, you enter the realm of Chord Chaining. The chord buttons change from plain green to many different colours so you can easily identify them within the chain, which is (you probably guessed) up to 32 bars long. The chain plays a single bar of each chord in a loop until you touch a key, at which point all entries are wiped! Chord chains are a superb sketch pad but, having lost a few accidentally, I began to yearn for a means of saving them, ideally on a per‑bank basis and with my eight stored chords included too. It seems like Arp is inches away from being a 16‑song backing machine so I was delighted to hear Midicake are considering some means of saving chains in a future firmware update.

MIDI Control

If the onboard modulation isn’t wild enough to cover all eventualities, you’ll be glad of the MIDI Learn function, which assigns Arp parameters to external MIDI control. I quickly drafted in some MIDI CC output from my Elektron Octatrack in order to lure Arp down the dark alleys of probability. I went on to remotely control Arp’s MIDI channel and automate precise instrument shifts for specific regions of a phrase, something that’s not so straightforward on Arp itself.

External control also means you aren’t limited to eight chord buttons but can dynamically populate the note pool from a connected keyboard or sequencer. Arp really shines when taking its input this way and lends itself to all manner of accompaniment duties, such as taking chords from existing songs to see what will emerge.

Arp is a flexible and interactive partner that in some cases could be an alternative to a sequencer.

Conclusion

It took me a little while to grasp the paradigm shift from familiar synth arpeggiators but the effort was worth it. After a few days, I realised that what is sacrificed in speed and simplicity is compensated for by the richness of the arpeggios on offer. Once familiar with the menu system, it isn’t too much of a chore to navigate either.

In general, I was reminded of what can be achieved by concentrating only on note pitches, velocities and lengths, and how rewarding it can be to divide arpeggios into separate components, perhaps spread across several instruments. Equally enjoyable, you can aim all four generators at a single synth and mute and unmute parts as you play. In this way, fed either by custom chords or manual input, Arp is a flexible and interactive partner that in some cases could be an alternative to a sequencer.

Admittedly, some of its features would benefit from further development but, equally, some are so novel I can’t think of equivalents elsewhere. The implementation of polyrhythms arrived almost as this review was complete but even in the short time I had, it was obvious this is going to open up whole new vistas of timing complexity.