Ruben and Serge Fernandez come from the French city of Tarbes located in the south-west of France nearby the Pyrénées mountains. In 1972, while they were building small sound devices they became acquainted with a Moog synthesizer and decided to build their own sound synthesizer. In september 1975, they moved to Toulouse to complete their academic studies : Ruben graduated in Computer Science (where he learned the Cobol programming language) and Serge graduated in Electric Engineering.  In a first stage they produced custom modules for their musician pals in Toulouse. The Série 11 modulars appeared in 1976.

VERTO, the french guitar player was one among the first users and contributed to the evolution of the Série 11 and also to the design of the keyboard version of the Kobol.
In 1976 they met Klaus Schulze who introduced the EMS synthi to them, and starting from that moment the design and production of their new systems were boosted. They created their company (a SARL) name RSF (the initials of Ruben Serge Fernandez) and production started in a small house located rue Claire Cazelles in Toulouse. About twenty modular systems (some of them housed in Samsonite suitcases) were sold accounting for a total of more than 300 modules. Next a series of master keyboards was also released among which a special portable model for Benoît Widemann (keyboardist of the famous French band Magma) that was customized to control Benoît's Minimoog. Benoît was also very committed in the development of all the synths of RSF.
The keyboard version of the Kobol appeared in 1978 and part of the external design is due to Klaus Blasquiz (lead singer of Magma). The woodwork of the very first models was made by Michel Chavania (also known for LAG guitars). Grey was the colour of the control knobs. The name Kobol comes from a small character of the German mythology. RSF aimed at the "top notch" market and the Kobol was clearly inspired by the Minimoog. As such, it was a real success and it's fantastic sound seduced  and convinced many professional musicians among which Jean-Michel Jarre, Kate Bush, Vince Clarke, Bernard Szajner, Vangelis and Peter Gabriel who actually came to try it after a concert in Toulouse back in 1980. The Kobol featured a very rare function : it was possible to sweep continuously from one waveshape to another, what we'd  call "wave-morphing" nowadays. Among the other features were : memories, sequencer, stable VCOs and a very musical filter. All these contributed to success, although it was difficult to get a part of the synthesizer market that was already dominated by huge American and Japanese companies. In France, the market was small and because of a lack of confidence and promotional means the sales remained rather low. However, with the next modular series sales started to raise.
The rack version of the Kobol was released in 1979. As a matter of fact it came in four different racks : the Kobol Expander that contained the synthesis voice only, the Programmer rack that contained the memory circuits and the Expander 2 rack where could be found some auxiliary modules that were not available in the original Kobol and eventually the KM-8 an eight voices mixer. The connections between modules were normalized but could superseded by external patches turning it into a genuine modular system. This made it very appealing for schools of music and electronic music composers. Meanwhile, RSF built a one of a kind mixing desk (TPU12)  for the recording studio Condorcet in Toulouse.

Fame occurred when Jean-Michel Jarre brought his huge RSF modular system on tour in China. By this time RSF developed a polyphonic keyboard, the Polyclavier. The Polyclavier was associated to four voices polyphonic systems based on Kobom racks in order to satisfy the increasing requests from musicians for a polyphonic Kobol. However, only five or six of these polykobol ancestors were built. With no auto-tune function and without polyphonic modulators these systems were rather limited.
In 1981, the Fernandez brothers splitted and they created separate companies of their own. Serge created RSF Sono in Toulouse, a small business of sono and lighting gear; where he also designed light show control desks. Ruben created RSF SA. Synthétiseurs in Saint Sulpice sur Leze and employed ten persons. They were meant to produce the Polykobol 2, but this model never showed up because of the difficulties of adaptation of the electronic boards of the Kobol. As a matter of fact, only one 4 voices prototype that was not even working and a wood cabinet.



Following the advices of many musicians among whom Benoît Widemann, the Polykobol 2 project was reactivated and eventually became more ambitious including new features such as a digital polysequencer, a dynamic keyboard, a K7 tape interface, more modulations and an arpeggiator. Unfortunately, RSF SA. did not have the finances to fully support the development costs. Furthermore, because of the design complexity (more than 500 parts including three 6809 CPUs), the electronics of this synthesizer was very unstable. Its release was postponed many times and this also delayed the development of other products. Only the Blackbox was released during this period, this device was meant to produce polyphony with a monphonic synth. It was hugely inspired by the EML Polybox and appeared to be a sale winner because of its budget price.

By the end of 1982, RSF SA is bankrupted and the ARIA society whose manager was Mr Baumesnil bought it with all the stock, half of the staff and the new prototype of the rhythm machine DD10 for a total amount of US$20,000. Ruben Fernandez became technical director and kept designing new products. The aim of ARIA was to diversify its assets and thus wished RSF to be a profitable investment quickly. The first Polykobol 2 were eventually shipped to their patient customers by the summer 1983, some of the latter did place their order and paid for it more than one year before. Meanwhile, the Polysequencer and dynamic keyboard did not work and the Polykobol 2 totally lacked of stability. Even though it provided marvellous sonic capabilities it was a complete commercial failure since its price of US$12,000 was for the happy few and at the same time Yamaha released the DX7 for US$3,000. The digital revolution was beginning... farewell analogue monsters !



In 1984, a series of digital rhythm machines is released: the DD14 and DD30 that provided with very nice functions and sonorities. Next in 1985 came out what was to be the best of the product line, the SD140 which just as the EMU's SP12 made it possible to record samples. A programme was also available on the ATARI personal computer to edit and store the samples. The SD140 was a real technological success and sounded great (and still sounds great). However, these models did not sell well and ARIA ceased the activities of RSF and Ruben Fernandez left the society in 1987.

Nowadays, RSF is a legendary trademark. The instruments bearing this name are very much sought after for their high sonic qualities and the scarceness of these machines made their prizes rise on the second hand market. Fame and recognition often come long after something has disappeared!