Mixing an action adventure show for children can present some interesting challenges, as London-based Company 3 Senior re-recording mixer Mathew Knights explains. The Famous Five anthology (loosely based on the books by Enid Blyton) recently returned to CBBC (Children’s BBC) for its second feature-length episode, Peril on the Night Train, the follow-up to The Curse of Kirrin Island, which dropped in late 2023. “You want the soundtrack to grab younger viewers’ attention,” he points out, “but you don’t want to terrify them.”

In this installment of the anthology, four intrepid young explorers and their dog combat dangerous characters and unusual mysteries that they take on together as friends. Peril on The Night Train is a cross-country adventure that kicks off when adult Quentin (James Lance) invents an amazing machine — a proto computer he dubs “the Algebra Engine.” With World War II in the offing, the clinging, clanking device is critical for the country’s counter intelligence efforts and this group of young friends must ensure it does not fall into enemy hands.

Sound editorial work for the Algebra Engine itself, he recalls, involves “sounds of cogs and keys and whatnot that suggests the sounds of a computer, while it is also very much a manual device — a bit like the Enigma machine,” he says of Britain’s top-secret World War II-era decoder that made significant contributions to the war efforts against the NAZIs. Subsequently, it will be stolen from the kids as they try to transport it by train to British authorities.

Naturally, building SFX for a device like this, “was about inventing a cranky, clunky thing. It also doesn’t exactly work perfectly, so we had to make the sounds it makes when it starts to break down a little bit. This was a mixture of all types of work with some bits from sound effects libraries of whirring machines and clocks and mechanical noises. And then we got the Foley artists to do some metal crinkling and crankling, rubbing different sized clocks together and then rolling bits of metal on each other and then,” — within ProTools — “we’d distort the sounds into a whole lot of raspy, weird noises. It was a mixture of elements that all went together and came out sounding great.”

Backgrounds and environments for the episode didn’t require a huge amount of period sounds since much of the story is set in a rural seaside village and on remote Kirrin Island and the Scottish Highlands far from period cars and machinery. “Quite a lot of the work was mainly about finding the right sea noises and wind and birds and other sounds you’d expect in this rural atmosphere.” The few vintage cars and trucks that had to be represented in the track, Knights notes, were a combination of the live recordings made of the picture cars during the shoot, and then, “we can also match specific makes and models of cars with number plate recognition and we’ll probably find recordings in Company 3’s large sound effects libraries, acquired over many years going back long before we were Company 3. I also have about five terabytes of my own sound effects, many of which are of cars from many eras.

“Characters do travel on old steam trains rattling over tracks,” he adds. “For that, we ended up using a lot of different train sounds, not necessarily being completely accurate with the specific train onscreen because a certain train noise might sound better from a different type of steam engine than the specific one onscreen.” The number of people who might notice the sounds aren’t from that exact train, he points out, is negligible at best. His goal is to find what works the best for the story.

A great deal of sound mixing is about ensuring that the soundscape doesn’t have too many frequencies at a given time fighting to be heard, and so that the most important sound, generally the dialogue, is clear of too many other sounds muddying the dialogue’s frequency range.

So, when prepping the mix (everything is done within ProTools), Knights explains, “When it comes to sound design I usually ask that the sound effects editors to give me material broken down into three elements — high frequency, low frequency and a low bass frequency.  Once I have those three elements, I experiment with them and choose which bits are better.  On TV generally, the higher elements come through better than the low bass elements, although in this case, some of the lower-end material turned out to be better to use because the kids’ voices, of course, tended to be higher.”

Knights mixed the show in 5.1 Dolby with the filmmakers always keen to hear everything in stereo, since that is the way, most viewers will hear it. While his brief was essentially to mix it the way he would a mystery adventure for adults, “there was a concern that we should be careful not to have too many big, loud scary moments. Even when things were big, loud and scary, we had to pull back a little bit because you don’t want kids watching it to jump out of their skins!”

Company 3 Senior Colorist Gareth Spensley handled grading these episodes mere steps away from the mixing stage at the same London studio.

The Famous Five: Peril on the Night Train and The Curse of Kirrin Island are both available in the UK on CBBC.