Just uploaded onto YouTube is an LP from the 80s featuring the Americans Ric & Dave playing Wersi instruments from that era. (Arrangers as we know today didn't exist and keyboards that were around were just the easy play features of an organ in a single keyboard box)

Enjoy

Interesting. Do you know if it‘s from the late eighties? Some of the sounds sound already sample-based...

1987/8

From the technical manual

The CD System With Full Digital Tone
Processing
In this new Wersi technology, a microprocessor system
computes all the sounds and digital.to-analog
conversion produces audio tones from the resulting
data. The processor system consists of a master
processor and up to eight co-processors, known as
slaves.
The slaves are responsible for the correct processing of
the tones, receiving essential data such as pitch, volume
(envelope amplitude), frequency, vibrato, formants, etc.
from the master processor. The master processor sends
new data to the slave anytime there is a change in input
status, whether it is a registration change or a new key
stroke.
The outstanding advantage of this system is that a wide
range of musical forms can be achieved, even though
the hardware never changes. It is the software-data pro-
grams read into the organ from a memory card or a
computer-that creates so many musical possibilities.
The data in the organ's memories can be added to or
changed completely, giving the organ a whole new
repertoire, if desired. Sounds from liturgical organ to
synthesizers to conventional musical instruments are
possible through software.
A further advantage of this system is that a given sound
quality, once achieved and filed as software, will be the
same when reproduced by any organ in the series, since
hardware variations will have virtually no effect on the
sound properties.
Additional special effects can be achieved through
further processing of the digitally developed voices via
a voltage-controlled filter (VCF) and a phase vibrato
(Wersivoice) circuit.
Apart from its contrast to other organ systems, the CD
concept offers the most possibilities in terms of sound
and functions, and is the most flexible concept for the
electronic production of individual musical voices yet
presented

NOTE: The drum soundsare samples

OK, so the other voices are obviously good FM-based voices.
Yes, I remember that end of the 80s the Yamaha organs started with drum samples first, combined with frequency modulation for the other sounds.

Yamaha did indeed use FM based sounds, however Wersi used Wavetables in their instruments (The other synthesis method that was in competition with FM at the time) to produce the sounds. (Hence all the processing and slave processors required)

Bill