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Korg KR-55 Pro

Rhythm Machine By Bob Thomas
Published November 2018

Korg KR‑55 Pro

Equipped with audio recording and playback and a four‑channel mixer, the KR‑55 Pro is more than just a rhythm machine.

Korg have maintained a long, strong and loyal commitment to the rhythm machine market, and their latest offering, the KR‑55 Pro multi‑function rhythm machine, combines the convenience of pre‑programmed, sample‑based rhythms with an SD card‑based audio recorder/player and a four‑channel on‑board mixer to produce a unit that is designed to meet the requirements of live performance, rehearsal and songwriting rhythm duties.

The Box

Many early Korg rhythm machines featured wooden (or wood‑effect) panels in order to match the cosmetics of the electronic organs of the day, and the KR‑55 Pro carries on that tradition. On the rear‑panel of its chunky chassis you’ll find a slot for an optional, though absolutely essential, SD card, the left (mono) and right outputs plus the input for the optional Vox VFS5 footswitch on quarter‑inch jacks, and two stereo mini‑jacks for the aux input and the single headphone output. Power to the unit comes either via a 9V DC external power supply or, for mobile use, from six AA batteries, whose remaining charge can be displayed across the first eight drum‑style select buttons.

The KR‑55 Pro’s front panel is oriented horizontally and is divided into four functional areas. On the left at the top, a balanced microphone (dynamic mics only) XLR connector and twin instrument inputs on quarter‑inch jacks sit next to two illuminated soft‑switch buttons that activate the on‑board silent tuning facility and Korg’s proprietary Acoustage function. Acoustage widens the apparent stereo width of the KR‑55 Pro’s main and headphone outputs, although the user manual does recommend turning it off when using headphones and notes that the effect is not recorded by the on‑board recorder. On the far right sits the unit’s illuminated on/off soft switch.

Next up is a row of rotary controls for the KR‑55’s on‑board four‑channel mixer. From the left, you’ll find the level knobs for its four inputs — the mic and two instruments plus the Rhythm/Play input. This latter input carries either the output of the rhythm machine or the audio being replayed from an SD card (which must be formatted on the KR‑55 Pro). Next comes the assignable reverb and the global treble and bass controls, the effect of the latter two being heard at the main and headphone outputs, but not recorded by the on‑board recorder. A master volume control completes the mixer strip.

On the KR‑55’s back panel we find 3.5mm headphone and aux in sockets, and audio outputs and a footswitch input on quarter‑inch jack sockets. On the KR‑55’s back panel we find 3.5mm headphone and aux in sockets, and audio outputs and a footswitch input on quarter‑inch jack sockets.

The Drums, The Drums

Three rows of eight illuminating soft‑switching yellow buttons allow you to access the KR‑55 Pro’s 24 eight‑bar, sampled drum/percussion styles. Each drum style contains a basic rhythm plus one variation, and two one‑bar fills, the second of which is used as an ending. These variants are accessed via the VAR(iation), the F(ill)1 and F2 and the Tap/End buttons in the control section that makes up the fourth, and final, front panel area. Rather disappointingly, from my perspective, there is no facility in the KR‑55 to create and store user patterns

The style selection on offer — all in 4/4 apart from two in 3/4 — seems rather limited and somewhat old‑fashioned to me, but others may find it more than adequate for their needs. The styles themselves are said to have been recorded live using Korg’s proprietary Real Groove Technology. This technology uses data recorded from (and I quote from the KR‑55 Pro’s web page) “actual professional musicians performing at various tempi”, and is said to “accurately reproduce the experience of playing with a percussionist.” The web site marketing speak also claims that “sounds, grooves and phrases will play back at pristine quality even if you change the tempo...” although the manual does warn that changing the tempo “...can cause the character of the sound to differ somewhat.”

In The Green

A fourth row of multi‑functional, soft‑switching green buttons marked M1‑M8 sit below the drum‑style grid. Their primary role is to display the measure (bar) of the selected style, variation or fill that is currently being played and to flash in time as a visual metronome. I tend to think in eight‑bar segments, and so I found its operation to be a bit confusing when playing it ‘live’ because, if I played a fill in bar four of a pattern, prior to a planned switch to its variation in bar five, the sequence returned to bar one (M1) after the fill. The reason for this is that M1‑M8 display the current bar of a style, rather than the current bar of an eight‑bar segment so, instead of watching bars five to eight pass by, I had to remember, for example, to play a fill again in the ‘new’ bar four to get me back to the start of another eight‑bar sequence. Each of these green buttons can also have a rhythm style variation assigned to it and instantly recalled and displayed when the button is pressed.

Apart from their percussion‑related duties, these green buttons are also used to select from the eight possible audio file playback folders, each of which can contain up to 99 files. The buttons also have a role in the tuner function as, depending which audible reference tone is selected, they can play the four open notes of a bass guitar, the six open notes of a guitar or a C‑major piano scale. In piano mode, the yellow button above M1 plays C#, the one above M2, D# etc, with the enharmonic E# and B# being missed out.

Control Centre

The fourth and final front panel sector controls the KR‑55 Pro’s functionality. On the left, a column of white keys selects the unit’s basic operational mode: Rhythm (playback of patterns), Recorder (records all inputs with or without a rhythm pattern or imported audio file playback to an SD card), Player (play, or record along to, audio files from SD card) and System — which allows you to select battery type (alkaline or nickel‑metal hybrid), to set the reverb routing (either mic only, input jacks 1+2 only or all three) and to set the automatic power‑off timer function and to format an SD card.

In Rhythm mode, not only can you control the playback of any selected rhythm style using the transport controls (Start/Stop, F1, F2, VAR and Tap/End) but you can also create a Chain, which is the rhythm track for an entire song. The KR‑55 Pro can store 30 chains, each up to 999 measures long. Rather inconveniently, the rhythm style, variant and/or fill has to be selected and stored manually for each individual measure, which is not the most time‑efficient method of building a rhythm track that I can think of. However, having built and stored your chain, you can then use it as a backing track either for live use, or for recording, where you can either record it and then overdub over it in Recorder mode, or you can record both it and your performance simultaneously in Rhythm mode.

In Recorder mode, you can either record a performance without rhythm backing (a metronome function, with nine possible time signatures (3/4, 4/4, 4/5, 7/4, 5/8, 6/8, 7/8, 9/8 and 12/8) is available) or you can overdub onto an existing song or imported audio file. When overdubbing, you can either drop‑in manually, or use the Loop/Auto function to go into record at the start of a loop (which you set using the M1 and M2 buttons to mark the start and end points) and go out at the end.

In Player mode not only can you replay 16‑bit, 44.1kHz uncompressed PCM WAV files from a KR‑55 Pro‑formatted SD card but also you can organise the files into up to 10 playlists, each of which can contain up to 24 audio files, a feature ideal for backing track setlists. The Loop/Auto key allows you to loop either one a single file or all files. Player mode also allows you to play along with an audio file from start to finish and to record the resulting performance, but not to drop‑in or overdub — if you want to do that, you have to import the file into the record function.

All recording data, from whatever operational mode, is stored on the SD card. It is not possible to remix a recording made on the KR‑55, or to export it to a DAW as a multitrack — all you can do is to convert your recording to a 16‑bit, 44.1kHz WAV file on the SD card and load it into your computer from there.

In Use

As a quick and easy‑to‑use rhythm machine the styles programmed into the KR‑55 Pro certainly have plenty to offer in terms of sound quality (Korg’s Acoustage stereo spread works superbly), rhythmic interest and groove. With the proviso that I could find a suitable style or variation, playing along to the KR‑55 Pro was an enjoyable and rewarding experience, and much better than any metronome, even the KR‑55 Pro’s on‑board 16‑voice version. Incidentally, I did find one small feature that doesn’t appear in the manual in that, if you start playing a style with a fill selected, the fill plays as a one‑bar intro, and if you then activate a different style whilst that fill is playing, the pattern proper starts at bar one with the new selection.

I also appreciated the KR‑55 Pro’s facility that enabled me to store my favourite style variation in the M1‑M8 memories, especially as the appropriate style key and variation indicator lit up on recall, which meant that I didn’t have to keep notes of which style was where. However, I was much less enamoured of the Chain function, as bar‑by‑bar programming on the KR‑55 Pro is a bit time‑consuming, especially since there is no way to edit a completed chain other than by deleting it and starting over. I would think that it would be much simpler simply to perform and record a song’s rhythm track ‘live’ and then play along with, or overdub, the result. It is a pity that the KR‑55 Pro wasn’t given USB connectivity and an editor/librarian program as that would have made building a set’s worth of backing rhythms much, much easier.

The KR‑55 Pro’s Recorder function was another source of personal frustration. The unit’s inability to power a condenser microphone is a strange omission given its price point and target market. Add in the fact that any tonal adjustment made to the microphone or instrument inputs is not recorded and that recordings can’t be exported as separate tracks, and you’re left with what is essentially an audio notebook, albeit one with a pretty decent rhythm machine included. On a positive note, the Recorder function is simple and quite intuitive to use, and is capable of delivering good results with a correctly‑positioned, decent quality dynamic microphone, despite its lack of recordable EQ.

Player mode, on the other hand, worked exactly as promised and I can see its Playlist function being extremely useful for replaying backing tracks created on the KR‑55 Pro, or elsewhere, live on stage. Finally, there’s the optional VFS5 footswitch to consider. Originally developed for Vox’s Valvetronix range of amplifiers, it gives you foot control of the KR‑55 Pro’s transport functions. Mind you, I’d have thought that a company of Korg’s size could have provided a footswitch overlay to display the KR‑55 Pro’s functionality.


Korg appear to be positioning the KR‑55 Pro as a multi‑functional practice/rehearsal tool and live performance partner for songwriters, soloists, duos or trios — roles which it is potentially well‑suited to fulfil. However, whether or not the KR‑55 Pro will match the needs of its target users will depend largely on their preferred workflows and rhythmic requirements.

If you think that a KR‑55 Pro might be right for you, I’d suggest that you explore its pages on the Korg website where you’ll find information about it, plus a range of sound samples and its user manual.  


  • Drum sounds are excellent, with Korg’s proprietary Real Groove and Acoustage technologies delivering as promised.
  • Simple to use and generally quick and intuitive in operation.
  • Solidly built to last.


  • Limited selection of rhythms.
  • No user rhythm slots.
  • Certain aspects of its functionality are inconvenient in operation.
  • No SD card supplied.


An easy-to-use, good-sounding, pre-programmed, sample-based rhythm machine that incorporates a four-channel mixer and an audio recorder/player to produce a practice, rehearsal and live performance partner aimed at songwriters, soloists, duos and trios.


£299 including VAT.