The MOS Technology 6581 Sound Interface Device: The Definitive Review (Part 1)
Sweet Sidsation
Over twenty years ago, in a period of surprisingly fertile creativity, I put together this medley of Commodore 64 tunes, set to classic 808 and 909 beats. I posted it on a forum and got enough praise to polish my ego and gain a sense of reward for my toils.1 But really, I just loved assembling a set of tunes that I loved and weaving them together with some standard-fare dance music drum programming.2 I was actually a thief - I’d heard a demoscene sidtune that leapt between 80s game classics as a medley and, having discovered a very particular version of Windows SIDplayer, realised that I could have an absolute ball making my own. My little rip-off leans heavily into the greatest of all Commodore 64 SID composers, Rob Hubbard. While it starts with Beer Station, a demoscene loop that’s wildly pleasing, it soon launches into Hubbard’s Thrust main theme before a sojourn through his Crazy Comets highscore salute and off into Tim Follin’s theme for Scumball in its entirety.3 This then fades to the majesty of Hubbard’s main theme for Delta, which starts out as just one channel before dropping in the rest for a run through the theme’s greatest segments. Then we’re off to the Netherlands for Hawkeye’s victory/game complete theme by Jeroen Tel and Charles Deenan under their Maniacs of Noise guise. And then finally, for a laugh, I looped the Turbo Outrun sampled drums, again from Jeroen Tel, as a kind of run-out credits sequence to keep up a sense of demoscene production in audio. It was amazingly fun to make, and almost accidentally, it manages to cover off a lot of what made the MOS 6581 Sound Interface Device so special. I got in most of its sonic spectrum and, thanks to the processing afforded by the DAW I was using, could present the SID as if it was a ‘proper’ synth. Not that it was ever anything but - where so much gaming hardware used Yamaha’s cut-down FM chips to provide a thin, tinnier version of its legendary DX-7, the SID was effectively uncompromised. It wasn’t the poor relation of anything, it was simply its own, glorious self.
It’s that sense of an entirely individual sound that grants the 6581 its legendary status. Other 8-Bit machines may feature similar capabilities, but none quite match the versatility, the extended features, the undocumented quirks of the SID. Tech details like pulse width modulation may not mean much, but the way it can evolve a sound as it plays, in concert with the chip’s legendary filter, is part of that essential, elevating difference. The madness of adding ring modulation betrays the designer’s real goal. Bob Yannes was making an entire synth on a chip, just a few years after leaving university. It’s perhaps the raw enthusiasm and obliviousness to boundaries, which are the finest aspects of youthful exploration, that hallmark the SID’s design. Bob went on to co-found Ensoniq and develop even more capable chips, but it can be argued none of them were actually ‘better’. The SID is simply that good. That’s not to say the Yamaha AY chips, or the sound sources of the NES and PC-Engine, were incapable of great music. They were fine, but I can’t say any of them offered the versatility for musicians to develop entirely distinct sonic styles as the SID. A perfect showcase for this is the second bit of SID adulation that I made, this 57-minute mix of SID MP3s shoved through an EQ and reverb.4 This is a much more comprehensive tour of golden-era game theme greats, and does a far better job of covering off my favourite artists. Starting with Martin Galway’s iconic Ocean Loader, it segues into Peter Clarke’s superb Ocean Loader 35 before landing at our first Rob Hubbard piece, Chimera.
Chimera holds an extremely special place in my heart, as it was the very first sidtune I ever heard, way back in 1985 - some 40 years ago. Starting out with a scratchy voice sample exclaiming game’s name, Chimera launches with a spiralling arpeggio that culminates in a signature Hubbard synth-tom fill, which is backed with a wild filter-and-LFO sound using an oscillator and the noise generator to create a ‘riser’ effect. Chimera then jaunts along as an upbeat, pleasing ditty with a classic 50s ballad bassline,6 as soft, rounded square waves sound out the melody. Between the bars and phrases are little extra touches - call and response adornments and linking sounds to add a sprinkle of variation and complexity to the central themes. Unusually, Rob devotes an entire channel to keeping the swirling arpeggios going throughout. These arpeggios only cease for the odd bridge or two, where LFOed chords are played across two channels, but for a few bars before resolving back into the main melody. As an introduction to the wonders of the SID, I can hardly think of anything better. Rob uses both the ring modulation and the LFO to affect sounds, the ring modulation creating the metallic, ringing quality you hear in so many of his tunes, with the LFO controlling the volume so sounds appear to flutter or stutter as their notes are held. And of course, there’s Rob’s signature, booming synth-toms. A staple that I’d come to absolutely adore, along with his soaring square-wave solos, the toms are what makes a Rob Hubbard tune undeniably Rob’s.
Contrast Chimera with Ocean Loader, or Galway’s opening theme to Wizball, and you’ll hear the sonic difference between artists. Galway preferred to avoid the ‘one-chip band’ approach of Rob Hubbard and instead treated the SID as a purist melodic synth; his greatest tracks have no percussion at all, just the wonderfully clean sounds of pure waveforms working together. The sonic purity lets Galway play with modulation in a more transparent and obvious manner - sounds interact as their modulations change, be that the pulsewidth or the LFO controlling any of its addressable parameters. In this mode, Galway gets the SID to sing with perhaps its clearest and most crystalline qualities. Few musicians use the single-channel arpeggiated chord trick7 with the transparency of Galway. His Ocean Loader deploys it with skill and uncommon taste. Equally uncommon and amazingly distinctive is Fred Gray’s theme for Mutants. This was a tune I came to in the 1990s. I do remember it in period, but it was only when listening with adult ears that it got its hooks in me. Fred effectively pulls a quasi-Galway style out of the hat to make a largely percussion-less musical journey that starts with an almost aquatic looping intro (making great use of ring modulation) with soundtrack-like deep notes to set off the atmospheric main loop. The piece then erupts into a winding sawtooth chorus that seems to swerve between prog and country in its phrasing, with the sharp melody contrasted with classic arpeggiated chords. It resolves with a towering, euphoric crescendo much like Follin’s Scumball, but from a year earlier. It’s such a strange, compelling piece of music and while it’s very much in the Galway mode, it’s very specific to Gray.8 Especially if you listen to his other work, like the equally dramatic and cinematic themes for Mission AD. One reason why Mutants has such a place in my heart is that it was the very first sidtune I processed with effects. Using a walkman and a Boss DD-3 delay pedal, I got my first taste of how a processed SID can sound so much richer than the raw chip output. The delay blended together those ring-modulated loops and arpeggiated chords into rich textures, with the melodies and solos ringing off into some vast cavernous space. It was almost revelatory, that a lowly home computer chip, presumably costing less than £20, could create such a landscape when brought into a bigger music production context. It was little surprise to me that Elektron would release the SidStation in 1999, a fully-equipped studio-grade module with the SID at its heart. Sadly, rather than ushering the SID as a rediscovered gem for general synthesis, the SidStation did more to popularise a consensus chiptune sound that evolved into almost a gimmick of sorts for the early 2000s, rather than opening up the SID for use as a serious instrument. In reality, the chiptune sound had evolved far earlier. You can hear a broader generalisation of features in the output of second-generation sidtune musicians. Compare tunes from artists that start after 1987 to those who predate that year and you’ll hear what I mean. The signature Maniacs of Noise sound palette is part Hubbard, part Galway. It tries to be the one-chip-band but adores pure notes and clean orchestration. The Hawkeye soundtrack is a perfect example here, and Jeroen does it again with Cybernoid 2, perhaps the slickest and most accomplished tune of the mid-late C64 era. While these are extremely good both musically and technically, there’s always the sense that it’s building on the work of the founding ancestors.
Speaking of which, my indulgent 57-minute mix features another of my all-time favourites, Rob Hubbard’s theme for Zoids. This is very much a re-arrangement of synth band Synergy’s Ancestors and for my money, vastly outclasses it. Rob uses amazing channel-packing and LFO effects to conjure the image of giant, lumbering war machines with a cover that’s far more kinetic and romantic than the Synergy original. As if powered by steam, Rob uses the noise generator to add percussive chips and hisses throughout the backing rhythm as colossal melodies play over the top. A superbly glissando-soaked square-wave solo screams through key changes that still catch me off-guard today. It’s a piece of such technical excellence that you’d be forgiven for thinking Hubbard had magically unlocked three extra channels on the chip, to the point where I literally did not care that it wasn’t 100% all his work. Also on the mix is his tune for Master Of Magic. Another Synergy cover from the same album as Ancestors, Rob reworks Shibolet into a surprisingly effective medieval round, complete with renditions of flutes, fiddles and various other period instruments alongside some very metallic percussion. Again, the realisation that this befuddlingly rich sonic tapestry is coming out of just three channels is a testament to Rob’s skill and talent. I can reel off Hubbard hits for days - the Monty On The Run highscore theme, Thrust,9 Delta’s main theme. Delta’s fucking tape loader!10 My mix ends with his main theme for W.A.R., a much more conceptual, progressive SIDtune that has a surprisingly funky breakdown halfway through. International Karate’s cover of Merry Christmas Mr Lawrence that busts out into a blistering cod-oriental boogie halfway through. And how can I forget the superb loading theme for Sanxion? Especially as it was the first sidtune I heard when I got my own 6581-a-like in a second-hand Commodore 128. I genuinely couldn’t assemble a playlist from his contemporaries that’s anywhere near as great or as varied. And for the wider body of artists, I’ve only mentioned Tim Follin passing but have completely ignored Matt Gray11 or Jonathan Dunn.12 I’ve also cruelly ignored Benn Daglish13 and David Whittaker,14 the ‘other two’ founding C64 musicians who, along with Rob Hubbard, were part of Zzap 64’s Musician's Ball feature. That piece introduced me to the first generation of truly accomplished C64 musicians, and I think it’s a testament to them, Zzap 64 and the SID that I can’t remember seeing an article about musicians for the Spectrum or the Amstrad, or pretty much anything, as it goes.
The real point in hand, of course, is that the SID in its various revisions and guises allowed musicians to flourish on the platform. It’s worth noting how incredibly difficult it was to make good music on that chip. Of the luminaries mentioned, nearly all coded their own music-making software, although plenty have talked about having to transpose ideas into the assembly language of the 6502 and the 6581’s registers, carefully inputting each individual note and all the synth parameters by hand. This gave an intimacy with the machine that even the most die-hard professional synth menu-diver wouldn’t be able to attain, and perhaps explains the fluency which Rob Hubbard and his contemporaries would eventually display with the SID’s full range of documented and undocumented capabilities. The virtuosity perhaps coincidental, but it can’t be denied that these cats could knock out a killer groove time and time again. Rob Hubbard may stand tallest for me, but it’s not by much. That particular cohort seemed to be surfing a tide that rose all boats, and presumably they swapped hints and tips with each other about the SID’s more arcane ins and outs. This seems to be hand-in-hand with the VIC-II knowledge that would see the Commodore 64 stretch so far beyond its on-paper limits that I’m sure the original designers would have refused to believe what they were seeing. Much as I couldn’t believe what I was hearing - and that I don’t mean the infamous volume-click digital playback that allowed the C64 to become a sampler. Digitised sound was always more a gimmick, a trick, than a serious musical utility. I personally couldn’t believe the funk, the momentum, the grace, the aural complexities. And of course, the weirdness. There’s something of the avant-garde with 80s sidtunes, particularly with the UK composers. The sense of experimentation, of riding the synthesiser zeitgeist of the 80s as novel synthetic sounds seeped into all media, is always there. In the SID’s case, its capabilities and extended features seemed more adroit to the task, more capable of performing those necessary and urgent experiments than the beepers, POKEYs, the AYs of other machines.
One of the first things I ever wrote in a serious, semi-pro capacity was an article on realtime music generation. I’d been dazzled by the PC Demoscene’s ability to cram a fully-fledged software synthesiser into a 64kb demo15 and with that 64 kilobyte limit stemming directly from the Commodore 64, the link back to the SID was visceral and utterly integral. My piece celebrated the idea that when a machine is playing synthesised music instead of a long digital sample, it’s like you’re hearing a live performance instead of a recording of one. And perhaps it’s in the sonic grandeur of the performance that the SID belts out its most sonorous notes. The power is in the generation of sound right in front of you, of hot rackets emerging from hot silicon as oscillators scream their per-cycle outputs in a dance far more complex and wondrous than a Fourier transform decoding a linear stream of numerical values. Of course, my remix and 57-minute mix are linear streams of numerical values, as are all the YouTube captures linked throughout this piece, but I hope the romance of the performance lingers with you, somehow. It was certainly part of the energy that flowed through whatever speakers you were hearing a Commodore 64 play its music through and given the bravura stylings of a blistering Rob Hubbard solo, I suspect he knew he was putting on a performance too. And that’s maybe the critical difference; where other sound chips played along with the game, the SID could always play to the audience.
[21]
Gary Liddon said it was brilliant and, quite frankly, that was more than enough to make me overjoyed.
Technical details are as follows: Sids and Drums was made in Sonic Foundry Acid, using Soundforge to edit the samples. Beats were made in Hammerhead and ReBirth, then sequenced and edited in Acid. there are two 909 drum loops and one classic Electro 808 loop, with additional single-bar loops of 909 handclaps, 909 rides, 909 crash and 808 maraca. Fills and builds were built by hand from the loops. The sidtunes were dumped with an old version of SIDplayer that allowed channel muting and WAV dumping, so the entire sidtune would be dumped three times to get a solo of each channel. These were then edited down into 16 and 32-bar loops in Soundforge, then re-assembled as the full tunes in Acid. This allowed me to run different EQ and FX on each channel, so I could boost the basslines without affecting other channels and add loads more reverb to the melody channels without swamping the song in muddy bass reverberation. It also let me solo out the key synth lines for iconic tunes like Rob Hubbard's Delta main theme and let its melody sing on its own in a wonderfully cavernous reverb, as the SID truly deserves. If you don't like reverb, you are a bad person. Junkie XL is on my side here and he had the maddest synth collection you will ever fucking see. The speech was attempted in a C64 emulator but the wave dump didn't work properly. The speech as actually done in a vintage speech-synth freeware program. Hilariously, while it was able to emulate a C64 hardware speech module, the freeware's interpreter was far too good and outputted natural-sounding speech, so I had to program it with phonetic sounds to approximate the wonky syntax of 80s speech synths.
Oddly free from any percussion at all, Tim's theme for Scumball is a soaring masterpiece of SID arpeggiation, which ends beautifully by using all three channels to deliver a surprisingly fat orchestra hit. Was great fun to add cheesy 90s dance drums to supplement Follin's rising crescendo. I took great pride in deploying the fabulous 'claps and hats' breakdown for the section comprised of single chord stabs and swirling arpeggios prior to the tune's climax.
Far less technical, this literal stringing together of MP3s with EQ, stereo widening and reverb was actually a remake (of sorts) of a tape I'd recorded in the mid-90s of sidtunes recorded from an Amiga running a nostalgic C64 jukebox demo that had ALL the classics. Somehow, via waveforms or something, the jukebox renditions sounded just as I'd remembered, only without the filtering. This tape was named 'Hot Rackets' after an infamous early-80s porn film that had done the rounds on a many-gen pirated VHS, and a friend used to listen to it while doing the washing up, bless him.
Mysteriously used by Ocean only a few times, notably for its conversion of Slap Fight, Ocean Loader 3 carries a weighty, Vangelis-like thematic quality, reminding me of the closing theme for Blade Runner. Peter wasn't exactly a luminary in the C64 music scene, but this tune sits alongside the arcade-perfect Bubble Bobble soundtrack as particularly accomplished pieces for the SID. Like Mark Cooksey, Peter Clarke is one of the undersung SID troubadours.
Something of an early Hubbard staple, the key thing about this style of bassline is the the notes fall only on the kick drums of beats 1 and 3 of the bar, allowing the channel to switch to a snare sound for beats 2 and 4. This efficiency in packing the channel is what allows Rob to devote an entire channel to keeping the arpeggios going. When doused in heavy reverb, this makes a glorious wash of swirling notes.
This effect, which sounds like a shimmering chord, is achieved by cycling through the notes of a chord on a single channel at rapid speeds, meaning the notes almost blend to form a chord yet remain separate sounds. A trick of the ear, it was adopted surprisingly early on the SID and is absolutely a staple of the contemporary 'chiptune' sound.
Fred can be seen talking a little about the Mutants theme in this absolutely lovely clip.
Worthy of deeper commentary, Rob's main theme for Thrust is again, an absolutely massive tune that really shows off the SID's extraordinary prowess. Great melodies abound but a standout feature is Rob attempting to recreate the sound of vinyl DJ scratching in the breakdown. Absolute badass.
The tape version of Delta features a set of Hubbard tunes broken into their elements, with four scrollable columns and a selector controlled by the joystick. The player can then sequence their own Rob Hubbard loading song! This was followed up with a lesser-known Maniacs of Noise version for Hawkeye.
Matt Gray's Last Ninja 2 soundtrack included a different loading tune for each stage, including a remarkable take on Bomb the Bass's Beat Dis.
Picked by Charlie Brooker for his Desert Island Discs, Dunn's format-spanning Robocop theme sounds the best on the SID (obviously). Dunn's Ocean Loader 4 is another fabulous piece of late-era C64 music, which first entered my ears while loading Operation Wolf.
Now (very sadly) RIP, Benn's work was just as distinctively individual as Rob or Martin's. Personal favourite is the soundtrack for The Last Ninja, which is a masterpiece in SID programming. However, Benn's collab with Hubbard for Auf Wiedersehen Monty is every bit as fucking amazing as you'd expect.
Perhaps more famous for that Megablast rendition for the Bitmap Brothers' Xenon 2, David Whittaker's tunes never did that much for me. Mostly I remember Panther for being quite cinematic, with some lovely SID sawtooth chords. Of course, David would find fame with Zombie Nation and Kernkraft 400's sampling of his tune from Lazy Jones.
This was the legendary Farbrausch and its equally legendary FR:08, The Product. Released in 2000, it managed to fit a multi-megabyte demo into 64kb complete with realtime synthesised soundtrack. Quite the achievement.