So, how do you make an analogue audio tape? Dave Denyer visits RecordingTheMasters in France to find out how it’s done

In mid-July (perfectly timed for Bastille Day) Dave Denyer headed over to the Avranches in northern France to meet the team at RecordingTheMasters and learn all about the tape manufacturing process.

RecordingTheMasters is a leading manufacturer of professional and semi-professional analogue audio tapes. Their tapes are used worldwide in major recording studios and, if you’re buying contemporary music on tape from one of the growing number of current audiophile labels, there’s a good chance it’ll be on RecordingTheMasters’ reels.

For many years, the company manufactured its tapes under the RMG brand.

Arriving in Avranches

But in 2015 it became part of the Mulann Group (which makes the magnetic strips found on smart cards, among other things) and was rebranded as RecordingTheMasters. So these days, Mulann is the company and RecordingTheMasters the brand for the audio side of the business. Together, they have almost 100 years of expertise in magnetic tape manufacturing.

Mulann is now the largest of the current three audio tape manufacturers worldwide. The other two are ATR in the USA, who bought the old Ampex equipment, and Capture (US-owned with a sub-contracting manufacturing company probably located in Australia), who have very recently started producing tapes based on the old ‘Zonal’ recipe.

“The name RecordingTheMasters was chosen to reflect the iconic history of master tape, while also encouraging the younger generation to produce new ‘masters’ for future generations,” says chairman and CEO Jean-Luc Renou.

In 2016 Renou was joined by Théo Gardin who is now the company’s sales director. “His youth is a benefit”, says Renou. “RecordingTheMasters is about the future as much as the past. Both analogue and digital recordings can be transferred onto tape. It has a unique quality, now and for the future”.

In fact, many people would probably be surprised to learn that magnetic tape is actually the best storage medium for music currently available. Current technology means that the quality of tapes being made today far exceeds that of tape’s heyday, to the extent that data can be stored for several decades, far beyond what digital and optical media offer today.

Out for lunch: Jean-Luc Renou (left) & Théo Gardin (right)

Discovering the full Mulann / RTM range

My first discovery: it turns out that Mulann manufactures a far more extensive range of tape than I realized. There’s 1/8” widths for audio cassettes, and then  ¼”, ½” 1” and 2” width reel-to-reel tapes for home, studio and professional use.  The company also manufactures perforated audio tape for the cinema industry (in 16mm, 17.5mm and 35mm widths), as well as the aforementioned magnetic strips used in the smart card industry. Oh and they also manufacture instrumentation tape used in scientific industries and the military.

Time for that mooted cassette revival?

The newest addition to the RecordingTheMasters range is the 1/8” cassette tape. Mulann don’t actually manufacture cassettes as such, only the tape pancakes, which they then send to a partner here in the UK who puts them into cassette shells to be sold as RecordingTheMasters cassettes. These pancakes are also sold to duplication plants for the production of commercial pre-recorded cassettes (so it seems the old cassettes really are making a comeback!).

Cassette tape manufacture presented the company with a new challenge. At just 1/8”, the tape is more fragile than its wider counterparts. What’s more, the tape itself uses a thinner substrate than the pro tapes and has no back-coating, so it’s flimsier and more challenging to work with.  That said, the new cassettes that are now being manufactured have a quality and consistency far in excess of what was achievable when cassette was a mass-market, mass-produced medium. So now there should be a whole lot less of having to wind unravelled cassettes back in with a pencil stub (ah, happy memories of teenage!).

The reel-to-reel range

RTM’s audio tape product range

RecordingTheMasters make five different tapes: studio masters SM900, SM911 and SM468, and long-play LPR35 and LPR90 (which are thinner versions of SM911 and SM900 respectively). Each has unique properties which differentiate their audio recording and playback effects.

Think of the SM911 as the archetypal master-quality studio tape with excellent all-round characteristics. SM468 is very similar in performance to SM911 but has improved resistance to print-through, making it the optimum choice for long-term archiving. SM900 has a higher saturation point and so is ideal for high-level recordings, but of course high-level recording increases the likelihood of print-through and so SM900 is less often used for long-term archiving.

These tapes are based on decades-old formulations or ‘recipes’ – referring to the specific mix of powders and chemicals used. Mulann has inherited the original formulas created by AGFA and BASF in the 1970s. Back then, the SM468 was one of the best tapes on the market. It was right up there with the Ampex 406 and 456, but those Ampex tapes suffered horribly from sticky shed syndrome, so the SM468 formula is the one that’s stood the test of time. It’s been manufactured under various brand names over the years (chronologically: AGFA, BASF, EMTEC, Pyral, RecordingTheMasters). However, RecordingTheMasters’ current tapes aren’t identical to these long-standing classics. They’re better. Over the years, tweaks have been made to the tape formulations and to production techniques to improve performance, whether that be high frequency response, resistance to print-through or production consistency. Production rejection rates have also improved as processes have been fine-tuned over the years.

How to make a tape: from vats of chemicals to a brand new blank master reel

The polyester base film

So, my burning question was this: how do you make a tape?

The audio tape manufacturing process begins with a tape base film (known as the substrate), which is essentially just a roll of clear polyester sheet. Its thickness and evenness are obviously highly critical, and thickness will vary depending on the type of tape being made (reel-to-reel versus cassette, studio master versus long-play). This base film comes on rolls of approximately 66cm in width, and these whole rolls go through the production process before eventually being slit down to the requisite tape width.

To the base film, layers of chemicals, powders, pigments, oxide particles, binders, backings and coatings are applied. First there’s obviously the magnetic layer, which holds the magnetic signal. This is typically (but not always) brown in colour and is a mix of solvents and oxide powder. The solvents are in effect the carrier or glue. (It’s this glue going sticky that caused the dreaded sticky shed syndrome in some vintage formulations.) In addition, most professional studio quality tapes also have a back-coating to make the tape more robust and less prone to stretching, and to give it more ‘grip’ on the tape mechanism. However, historically, cheaper consumer open-reel tapes and cassette tapes didn’t tend to have a back-coating.

The powder room

The first port of call is the powder room – though obviously not in the usual sense of the term! The powder room is the place where you’ll find all of the basic raw materials required for tape manufacture: everything that will be applied to that tape base film to create the finished product. Barrels of chemicals, powders, pigments, oxide particles, the component elements of binders, backings, coatings etc. This room is very smelly and in fact is classified as a hazardous environment so special protective clothing has to be worn.

Above we can see four brown oxide magnetic pigment canisters, alongside drums of chemicals and solvents – both new and recycled (more on which later)…

Preparation and mixing

And so to the process of preparing the various ingredients: grinding down the oxide particles and mixing the chemicals (pigments, solvents, binders, etc).


In the case of studio master audio tapes, these ingredients are for the two layers that will be applied to the polyester film base: the magnetic coating (oxide layer) and the back coating.  I should add that not everything is mixed all at once, given that each concoction is prepared according to highly specific formulations. The oxide powder is ground down in massive machines to the very finest powder. It’s then mixed with solvents to produce a ‘slurry’ that can be accurately applied to incredibly fine tolerances.

Applying the coatings

Believe it or not, there’s actually a tape coating room! This is a massive room housing ‘E9’: a gargantuan machine some two-stories high – bigger than several double decker buses! The E9 coating machine was shipped over from what was the old EMTEC factory in Holland (when the AGFA/BASF/EMTEC business was bought by French company Pyral some years ago, before being bought by Mulann, many machines were shipped over). This is where the polyester film substrate is coated with the magnetic oxide layer and (where relevant) the back coating. A high precision ‘coater’ allows the tiniest adjustments to be made so that coatings can be applied to the finest tolerances. For example, the thickness of the magnetic coatings applied to the SM468 tapes is 14.5 microns (a micron being one-thousandth of a millimeter). That of the SM911 is 16 microns, and the SM900 is 19 microns. The back coating thickness varies from 3 microns on the SM900 to 4.5 microns on the LPR90. So the coating machine needs to be able to coat a continuous sheet of 66cm wide at an accuracy of at the very least half of a micron, or 0.0005mm. Adjustments can be made in real time to ensure that exactly the right amount of coating is applied, and that it is consistent across and along the entire roll. Coating is done in batches, one side at a time: first the oxide layer and then (where relevant) the back coating.

E9 Coating machine

Drying and calendering

The coatings are applied at one end of the lower level of the machine, then the freshly coated tape (still wet) is diverted to the upper level where it passes alongside magnets which align the magnetic particles within the still-wet oxide layer such that they’re all facing ‘north-south’ (so to speak). Once on the upper ‘deck’ (shown in the photo – opened for service) the tape then passes through the drying chamber. Throughout its journey through the machine the tape is supported on a cushion of air. During the drying process, most of the fluids (solvents) used are extracted and recycled. In fact around 90% of the total fluid used is recycled.

Finally, at the far end of the drying chamber the almost-(but not completely)-dry tape passes through the ‘calendering rollers’: highly polished heated metal rollers that apply pressure and heat to ‘calender’ the tape: making it smooth and giving an almost polished, shiny surface.

At this point the tape is still a 66cm-wide sheet. So the completion of this part of the process results in rolls of tape, 66cm wide, of varying formulations and thicknesses. These ‘jumbo’ rolls are now ready for ‘slitting’ – in other words, being cut into the various required tape widths.


In many respects the slitting process is the most impressive, as these 66cm wide rolls of tape are slit into the various widths.

Different machines are used for different tapes: the perforated film used in the movie industry is slit on one machine.  1/8” cassette tape is slit on another. There are two ¼” machines, because a separate machine is required for trident reels than for NAB hubs. Another audio tape slitter covers ½”, 1” and 2” tape.

Extreme precision is required here and the quality of the slitting can clearly be seen in the final pancakes which are perfectly flat (as the proverbial pancake).

Initially the sheet of tape passes over rollers etc until it reaches the knife block (‘before’ image below). The machine shown is used for slitting for 1”, 2” and ½” audio tapes. Here, the jumbo roll is being slit (in this case 1” tape).

From the knife block it is then separated into two parts, alternate slit tapes being diverted up and down (‘after’).  This is so that each tape is kept perfectly flat, and doesn’t rub against its now departed neighbour.  From here it is further diverted to allow sufficient separation between each tape so that the final carrier, be it a NAB hub or a trident reel, can be accommodated. It’s for this reason that many separate slitting machines are required.

The photos below shows the very cool trident ¼” slitting machine; in the third image (far right) the tape, which has already been separated up and down, is then directed left and right to create four ‘fans’ of tape heading to the receiving trident reels.

The individual tapes are appropriately spaced ready for their carriers (reel or hub), as they pass onto those carriers.

The machine pictured below is for ¼” tape on NAB hubs (used for reels or pancakes). You can see where the NAB hubs go on the bottom of the picture (ball bearing hub holders with blue / yellow flashes).  A 66cm wide jumbo roll will slit down to 100 rolls of ¼” tape (allowing for about 3% waste).

1/4″ slitting NAB

As well as trident and NAB hubs, RecordingTheMasters will occasionally produce a batch of AEG pancakes at the request of a customer (an AEG hub is an old type of pancake centre which isn’t much used these days, so they only make them on request rather than as standard).

Tape erasure

Once the tapes have been slit and loaded onto the receptacle – hub or reel – they are then bulk erased: passed though a tape erasing machine to ensure they are completely blank (silent). Otherwise stray fields encountered during production could add noise (hiss, etc) to the tape as it passes through the various machines.

After slitting, the tape is erased and then awaits packing


Finally, the tapes go to the assembly room where (if appropriate) flanges are screwed onto the hubs to create the popular metal NAB hub reel.

Assembly room with finished reels of SM900

Beyond audio tape

“Take me to your leader”: the perforating robots

As previously mentioned, in addition to audio tape for cassettes and reel-to-reel, Mulann also makes perforated audio tape for the cinema industry (in 16mm, 17.5mm and 35mm widths). These tapes are prepared and slit in a similar manner to the other audio tapes but then they go into the ‘perforating room’, which becomes a very noisy room when the precise sprocket holes are punched.

These sci-fi looking machines look like robots and here can be seen with blue leader tape.

Another additional process is required for instrumentation tape, which is used for scientific purposes and the military. It’s the ultimate quality tape and after slitting / erasing etc it’s burnished to give a super-smooth, polished surface.

The instrumentation business is hyper-demanding and so the processes involved in manufacturing this tape must be of the highest attainable quality. Those processes then trickle down to the rest of the Mulann range, which ensures the best possible products, right down to cassette tape.

R&D & quality assurance

Alongside Mulann’s production facilities I was also able to visit a number of other highly important areas.

Below is the laboratory where Mulann’s chemist works, testing new materials, processes, formulations, dyes etc.

Lab (chemist)

And the all-important quality control area. Here, samples from each batch of tapes are rigorously tested.

Each type of tape is played back on a carefully calibrated deck (or cassette player in the case of cassette tape) which is connected to a computer loaded with an Audio Precision test suite to ensure that the tapes’ performance is exactly to specification.

Optical testing is also used, in which the tapes are examined over a light box to check for any microscopic flaws in the oxide layer. These are just two examples from a list of many quality assurance processes which are performed by both humans and machines to check consistency and to ensure that production processes as efficient and effective as possible.

These processes are constantly being monitored and evaluated for potential improvement. A recent amendment was the addition of further slitting machine cleaning processes, in order to reduce dust generated by the slitting process. So the quest for improvement never stops.

And you may be reassured to know that all of the production machines are not currently running to their full capacity, so the potential is there to increase production five-fold as the market for tape grows!

And finally, the two warehouses: the first for goods-in where supplies and raw materials (flanges boxes etc) are kept (shown left below), and the second for stock and completed orders (right).

So, almost at the end of our tour. One last place to visit the sales department where Théo and his team take orders and serve RecordingTheMasters customers right across the globe.

Sylviane Annoh in the sales office

My sincere thanks to everyone at RecordingTheMasters for their time, their openness and their very warm welcome. It was a fascinating and hugely enjoyable visit. And now, at last, I know how an audio tape is made. Result!

Discover more about how analogue tape is made at