These instruments from 1981 were the first portable fullsize instruments with versatile "auto bass chord" accompaniment and belong to the last analogue keyboards created by Yamaha. Technically they were the direct successors of the Yamaha PS-2 hardware and have nice analogue timbres, arpeggio and unusual analogue percussion.

Yamaha PS-30

(pictures taken from eBay)

main features:

• 49 fullsize
• built-in speaker
• 10 note polyphony (only 4 notes with accompaniment)
• 4 note polyphonic chords
• monophonic solo voice
• 10 semi- OBS preset orchestra sounds {organ 1, trumpet, clarinet, piano, accordion | organ 2, string, oboe, harpsichord, vibraphone} selected by 5 OBS buttons + bank switch button
• 8 semi- OBS preset solo sounds {violin, trumpet, trombone, piccolo | saxophone, guitar 1, guitar 2, funny} selected by 4 OBS buttons + bank switch button
• 8 semi- OBS preset rhythms {march, waltz, tango, rhumba | disco, rock, swing, samba} selected by 4 OBS buttons + bank switch button
• locking multi- contact push button switches to select sounds and rhythms
• sustain switch
• fingered & single finger chord
• "chord memory" switch (means simply that chord is held when releasing keys)
• 2 bass variations ("multi bass")
• 2 arpeggio variations
• rhythm "8 bar variation" switch (inserts a fill-in every 8th bar)
• tempo slider
• separate rhythm, chord, arpeggio and solo volume sliders
• All main voice timbres seem to be made from a mixture of multiple analogue filtered squarewaves with a common digital envelope.
• analogue percussion {base, snare, hihat, low & high tabla(?)} sounds rather unspectacular, although possibly more realistic than many other analogue percussions. The hihat is likely mixed from 2 digital shift register feedback noise outputs at the CPU. The base is a dull popping noise.
• CPU "Yamaha YM1011, 16 2056" (40 pin DIL) + separate sound chip "Yamaha YM1101 E, 16 1853" (40 pin DIL).
• solo voice CPU(?) "Yamaha YM1102 F, 1Z 2258" (24 pin DIL) + sound chip(?) "Yamaha YM-1002, 1Y 20 28" (16 pin DIL) + filter IC "1G02611, 112 400" (14 pin DIL)
• solo voice tuning trimmer
• jacks for AC adapter, headphone, cinch sound input(!) & output and "expression" volume pedal
• internal power supply module that plugs into the battery compartment

eastereggs:

• 22 additional rhythm combinations are selectable by simply pressing multiple rhythm buttons!
• 12 higher note keys addable
• solo voice select buttons and its ensemble button make great filter sweeps when pressed or trilled during play.

notes:

In the case bottom is a groove to store a metal bow that can be used as a note stand. Like with the Bontempi Minstrel Beta, instead of a battery holder (mine is missing) a special power supply module PP-1 can be inserted into the battery compartment. Very bizarre is that the volume and tempo sliders work "wrongways", i.e. pushing them up makes sounds quieter or tempo slower, while pulling them down makes sounds louder and tempo faster. Likely sound mixers and graphic equalizers were so uncommon at that time that the control panel designers didn't come in mind to standardize this. Also the locking switches have an odd shape; they have a pivot at their rear end and tower up only with their front end when not pressed. I never saw such buttons at any other keyboard; possibly their design was inspired by piano keys. Also the golden "YAMAHA" logo at the front edge below the keyboard looks noble and piano- like.

The polyphonic "orchestra" preset sounds of the PS-30 feature many different vibratos; unlike with the Yamaha PS-2, the vibrato of "trumpet", "string" and "oboe" are delayed and fade in only after the sustain phase of the envelope begins, and even the accordion has a very shallow version of this vibrato. The "organ 2" has an undelayed medium speed vibrato, and the "vibraphone" has a rather strong and much slower vibrato. When a key is trilled with sustain, each new note occupies a new sound channel, which produces a great phasing sound and volume increase effect although this eats up polyphony. The sounds are based on squarewave tones with different pulse width, those are post- processed by different analogue filters, but unlike many early Casio keyboards with filtered squarewaves, the tones of this instrument are not just muffled duller but differ a lot in timbre, and regarding the technology they are even reasonable realistic. Only in the bass range many sounds turn into a more or less buzzy, sonorous purring drone, but this is a characteristic style element of squarewave based instruments. Such basses can resemble some of the famous POKEY sound effects on Atari XL homecomputers and are very different from the gradually duller and duller growing sine wave bass behaviour of average Yamaha FM keyboard sounds, but unlike e.g. Casio MT-60, the PS-30 features no really dry and creaky bass timbres but plays rather round and sonorous ones. Particularly the "organ 2" has a wonderful "black", droning squarewave bass, which is likely also enriched by the zipper noise of its digital vibrato. The "organ 1" sounds like a reed organ. The "trumpet" is duller(!) than "string" and should be better labelled "cello". The "piano" is a little dull and the "harpsichord" is harsh, a little thin and suffers from a slightly too slow attack rate which makes the envelope less credible. The "vibraphone" otherwise is a highlight of this instrument; it sounds great and (besides bass range) astonishingly realistic, although its sustain can not be turned off. The "oboe" sounds thin, but that is what it should. Also the "clarinet" is ok.

The "solo" preset sounds can be layered with the "orchestra" sounds. The solo sounds are only monophonic but include an analogue low- pass filter with decay envelope, which permits more realistic and expressive timbres. E.g. unlike above, the "trumpet" here really resembles what it was supposed to be. The trumpet and trombone fade duller and include delayed vibrato. Also both guitars fade duller; "guitar 1" is a dull one while "guitar 2" has a brighter timbre with some vibrato. The violin also employs delayed vibrato and sounds quite realistic. The saxophone has a mild, delayed vibrato. The "piccolo" is a sweet analogue tone with quite strong vibrato, that fades slightly duller; it doesn't sound really like a flute, but almost voice- like and resembles more a theremin or singing saw and gets a little brassy in the bass range; this cute and cheesy analogue timbre is definitely one of the great highlights of this instrument. The "funny" sound is a sort of e-bass with tuba timbre that fades brighter and has a strong vibrato. Interesting is that also in many early Casio keyboards (see Casio MT-60, CT-410V, MT-70, MT-30) sounds with "funny" in their name exist. The sustain button affects only the orchestra section but not the solo voice. There is a separate solo volume control and 2 "ensemble" switches to enable solo and/ or orchestra section separately. Unfortunately the solo section can not be used for a key split mode but only layered with the rest.

The analogue percussion sound a bit dull, but has an unusual timbre. The base is just a dull and quiet "pop" noise (like heard in the speaker when switching a radio on) consisting of 2 pulses muffled by a capacitor. The 2 tuned drums (tablas?, or congas??) have a strange timbre between drumming on empty plastic bottles and ceramic jugs. The hihat seems to based on a similar semi- digital technology like with the Yamaha PS-2 and sounds a bit more metallic than the analogue transistor noise ones found on other electronic percussion of that era. With the "8 bar variation" switch, an automatic fill- in is inserted every 8th bar of the rhythm; a manual "fill-in" button would have been much more useful. The default tempo settings of the individual rhythms seem to vary quite extreme (caused by different internal pattern resolution?). Likely to compensate this, the range of the tempo slider is quite wide, thus it needs to be tweaked with care because the tempo reacts audibly already on very small changes. In spite of this, the maximum tempo of some rhythms can not be set really high.

The "chord memory" switch makes simply that current chord is held after releasing the chord keys (this is no sequencer), but unusual is the way how rhythm and chord memory interact. The rhythm is activated here by 2 different locking switches; when only "start" is on, rhythm plays always and independent from the chord section. When also "synchro" is on, rhythm is started as soon a chord key is pressed, and then keeps playing until rhythm is switched off. But when only "synchro" and not "start" is on, then the rhythm pattern starts as soon any chord keys are pressed, and so far chord memory is off, the rhythm stops each time you release all chord keys; this permits interesting improvisations e.g. by trilling on chord keys. This odd mode I yet only found at a single other and also very old keyboard, namely my Bontempi Minstrel Beta. Unlike the latter, the chord memory here works only with the automatic accompaniment and not in organ chord mode (with rhythm stopped). In fingered chord mode the accompaniment plays the more notes the more keys are pressed, and this works even perfectly with all key combinations (up to 4 keys) and not just the few ones establishment has defined to be "chords", which permits very versatile accompaniment sound patterns. (This flexible behaviour is absolute no matter of course, see the later Yamaha PSS-390 for an annoyingly stubborn example.) The "multi bass" button changes the accompaniment; with most rhythms it makes a walking bass pattern. When no rhythm is selected, the instrument plays instead of accompaniment plain organ chords with a fixed timbre and a little sustain. The arpeggio has a decay envelope (like a harp) and the notes it plays change by the currently pressed accompaniment keys (but the count of notes stay the same). Its variation switch switches with most rhythms between a 16 step and an 8 step arpeggio pattern; only with "rhumba" it changes the speed.
 

Yamaha PS-20

(picture taken from eBay, showing my specimen)

In my childhood my she- teacher owned this keyboard and she also took it with her into a hostel during a school travel where our class could play on it. As a little school boy with only a monophonic transistor toy organ, this fullsize instrument with its golden "YAMAHA" logo at the front appeared so huge and impressive to me like a concert grand piano, and it also became my 1st experience with arpeggios and automatic accompaniment. I first had bought a Yamaha PS-20 at eBay; the PS-30 seemed to be so unbelievable hard to find that it was fully out of reach and rather a "rumoured to exist" - not even Yamaha had listed it on their manual download site until I asked for it. My PS-30 has also the original brown imitation leather carry bag from Yamaha. The PS-20 seems to be much more common.

Such a dual colour button style on a beige case was also used on the Casio MT-60, although its controls are rounder.

(Caution: Both the Yamaha PS-20 and the PS-30 suffer of a really annoying disease; the foam rubber pods under their case dissolve into a tar- like, very sticky black goo. The only cure for this is to remove the black pulp from the pod holes at the bottom using a lot of Q-Tips and isopropanol (which still needs quite a lot of time), because otherwise it infests everything with black stains those at least on fabrics are almost impossible to remove. I had ruined a carpet floor with this stuff and could only get it out by rubbing it quite long with vegetable food oil and then removing this goo with concentrated liquid soap followed by plenty of water.)

A shorter 44 keys case variant of the PS-20 with only 6 sounds, 4 rhythms and far less features (no arpeggio...) was released as Yamaha PS-10, but this one is a totally different hardware class because it was instead just based on Yamaha PS-2 hardware. Already in 1982 Yamaha abandoned the analogue technology entirely and thus made all following keyboards only with strictly digital sound generation, while Casio kept analogue percussion and filters in their instruments far longer until the mid of 1980th. Nowadays the Yamaha PS-20 seems to be quite rare at eBay, and the PS-30 seems to be even extremely rare. Successors of these instruments were the Yamaha PS-55 (stereo) with the simplified variants PS-35 (stereo) and PS-25 (mono) from 1983, but these boring rectangular silver boxes with bulky speakers left and right to the keyboard were already digital (apparently based on Yamaha MK-100 hardware).
 

removal of these screws voids warranty...
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