In the mid-80s, my favorite synth manufacturer Siel found themselves in dire straits. Their marketshare was dwindling after the digital revolution kicked off by the DX-7, and their product line was poorly received overall. The DK-70 was an obvious knock-off of the Korg Poly-800, and they suffered from a somewhat deserved reputation for poor quality of manufacture, as did their fellow Italian brand Elka. It was around this time that they began taking on contract projects for other companies, in this case the musical instrument division of Suzuki. This isn't the same Suzuki who manufacture engines, but instead the company which runs music schools all over the world which teach the 'Suzuki Method', which is apparently a very regimented approach to learning to play a variety of instruments. It's been well-known that Suzuki distributed the Siel MDP-40 under their own label as the Suzuki RPM-40, but it turns out that Suzuki actually contracted Siel to design and manufacture a series of PCM home keyboards with some fairly interesting (and distinctly Siel-esque) quirks.
The Suzuki Keyman PK series consisted of at least the PK-49, the PK-61, and the PK-61ex, although there may have been a PK-88 with full weighted keys, but I believe that model was created by a different company. The initial shortcomings of the PK series were... interesting to say the least. The keyboards were produced from around 1984 or 85, but there is so little information that I can't be sure. The first models featured a standard array of sound outputs and a Siel-style 5-pin pedal input, as well as a switchable 5-pin DIN port which functioned as an RS-422 port, compatible with the serial port on the Commodore 64 among others. When switched, the port would communicate with an external box (presumably sold separately, I've never seen one) which would give the PK-49/61 a MIDI IN and OUT port. Apparently there was some learning software for the C64, which both trained you in the Suzuki Method and offered the ability to sequence your own songs with the internal sounds of the keyboard! Of course, this software, as with the MIDI Box, would seem to be totally lost to the ages.
The internal sounds were PCM-based, although with the RPM-40, as with the PK-49/61, the bitrate was stunningly low. The sounds of the MDP-40 I owned several years ago were so grainy and the sample time so short, they sounded roughly as close to a Roland TR-505 as a Boss DR-55 sounds to a TR-808. These poor quality samples were omitted in the rhythm section of the first series PK keyboards, which actually feature a fairly nice analog sound, although unfortunately not externally programmable (at least, not without the MIDI interface, the capabilities of which I do not know). On the other hand, the internal sounds are of the same vintage and the same strangely poor bitrate encoding standard. This makes them oddly difficult to differentiate from many other lower quality synthesizers of the time (digital or analog), which could provide for some interesting uses were the greater production use of these keyboards not mooted by the fact that they cannot be controlled by MIDI outright. The internal accompaniment patterns are excellent, not too over-orchestrated as Casio's tended to be, and the beat patterns are very similar to those of the MDP/RPM except more complex, perhaps owing to the larger ROM necessary for the accompaniment patterns. There are also individual volume controls for the rhythm, accompaniment, arpeggiator (patterns vary based on the drum/accompaniment selected, sound doesn't seem to), and the master voice. There is also a real-time two track sequencer, similar to the one in the DK-70.
The PK-61ex is a tremendous improvement over the first series, with internal MIDI i/o, higher quality PCM voices (definitely still 8-bit, but up there with the Mirage), and a fully PCM rhythm section with higher quality voices taken from the MDP/RPM. The sounds are still somewhat staccato, and the cymbal/hats are probably the only digital drum cymbal samples which are worse than the Yamaha RX series, but the snare, kick, and various other percussion sounds are actually extremely warm and punchy. There is even a separate output for the Drums! The 61ex also offers a manual drum switch section, which turns the top octave of the keyboard into a drum kit. I've yet to experiment with the MIDI to see whether the drum sounds can be played from an external source or if the internal patterns can be synched to MIDI clock, but I will update this post once I have. There are 14 internal sounds with sustain and a 'duet/quartet' function which doesn't seem to actually change the sound at all (maybe it was intended to stack voices as one would on an analog synth? sample based voices don't really seem to work like that though), and 14 rhythm/accomp patterns, with switchable percussion, hand claps, fill-in and break functions. There are two variations on the accomp. for each pattern, each using a different sound, as well as two variations on the bassline which also uses two different sounds. The arpeggiator would seem to just be the same somewhat analog blip sample. When turned on, the keyboard split uses the note or chord played on the bottom two octaves to drive the internal accompaniment and the upper three (or middle two if manual drums are also on) to provide voices, which are limited to the upper octaves. There is a Transpose function, but I don't know how it works as it doesn't seem to function on my 61ex. The internal accompaniment also features a 'simple chord' function which acts similar to the old Casio Chord function while active, otherwise if off the accompaniment functions very, very well as a compositional aid.
The internal sounds themselves leave quite a lot to be desired, even with the higher sample quality. The organ sounds are superb, as are the music box and vibes patches. The 'Harmon.' sounds a bit like a cross between strings and a chorus, but not intentionally. The trumpet, flute, clarinet and violin are absolutely terrible. The El. Guitar and Synth are both mediocre. All sounds have vibrato which can't be turned off, but is quite musical for the most part. The internal speakers are surprisingly warm and powerful, and they make the keyboard sound absolutely amazing for a mid 80's PCM home keyboard. Through the phones output, on the other hand, the sound is bizarrely different and extremely disappointing. I've yet to test the stereo and drum outputs through a mixer, and they may be run through some kind of resistor in the circuit. My PK-49 arrived with a short, which required you to pull the AC adapter input down in order to get power to the drum machine & accompaniment, but the PCM section worked fine! Classic Siel design, be prepared for it if you find yourself faced with one of these old keyboards.