Spectrum Music: Bleepin’ all over the world…

I got my first Spectrum under the Christmas tree in 1984, and from the moment I opened the box, I was completely smitten. It came with a six pack of software, most of which I ignored so that I could play my two new

favourite games: the racing sim, Chequered Flag, and a game that was part Frogger clone and part top down vertical scroller, Horace Goes Skiing. Now Horace demonstrates some of the challenges of trying to squeeze both sound and gameplay out of the Spectrum at the same time. Remember that programming calls to the beeper, tied up the main processor, freezing the action in the game. And so, in those early titles, music if it featured at all, was generally reserved for the title screens and in game sound effects were used sparingly.

In the first stage, as Horace tries to cross the busy road to collect his skis, you can hear a series of broken minor seventh intervals that are used to suggest traffic noise. [VIDEO GAME SOUNDS] That sound effect is quite a simple one, but the way that it’s executed is quite sophisticated. What you hear it is a tone of around 20 milliseconds duration, followed by a silence of equal length, during which, all of the game processing is carried out. That combination of fragmentary tones and perhaps more importantly, the gaps between ensures that the processor time is distributed between the sound effects and the gameplay.

There’s a single event driven music cue in the game which occurs when Horace is struck by a vehicle while crossing. Here, a simple note sequence based on a series of descending perfect fourths is triggered and the gameplay halts before an ambulance accompanied by a slower version of the traffic sound effect rolls across the bottom of the screen.

The skiing sequences use only simple beeps, most noticeably when Horace misses a gate, tying up the processor and halting the game for a second or two.

You can see the effect that it has on the smoothness of the gameplay.

One of the games I remember most fondly is Manic Miner, a game that became a runaway success and introduced the spectrum’s first truly iconic character, Miner Willy. Manic Miner was based on Miner 2049er, a platform game for Atari’s 8-bit systems that featured a Canadian mountie, Bounty Bob, who has to navigate his way through 10 different screens before his oxygen runs out. Several elements of Miner 2049er appear in Manic Miner.

The underground setting and the oxygen level as a timer, for example, but in creating Miner Willy, Smith injected a particularly British spin on the game with an absurd humour to the level and character design and a Pythonesque boot, a reference to the surreal 1970s comedy series which descends to squash Willy when the game is over. To squeeze music into the gameplay, Smith extended the idea behind the traffic sound effect that we heard in Horace Goes Skiing. He used a software interrupt to split the processor’s time between the gameplay and the sound playback routine. Each time the main game loop executes the programme branches out to play a very short fragment of sound before returning to carry out the game processing.

By carrying out that process over and over again, Smith built up an in-game melody from these sound fragments. In a thematic nod towards the game narrative, Smith chose an eight bar phrase from Grieg’s In the Hall of the Mountain King as the music to accompany the gameplay.

But Smith also realised that rather than simply playing an in-game melody, that approach made it possible to trigger sound effects simultaneously with the music by alternating between them, slotting each fragment of the sound effect into the spaces between those of the melody. Manic Miner has one main sound effect, the jump sound which uses the familiar sound metaphor of a rising and falling pitch contour to suggest a sense of motion.

Now we’re not quite finished with Manic Miner. Not content with introducing in-game music and sound effects alongside gameplay, Smith also discovered a way of squeezing two channels from the single channel Spectrum speaker. When it loads Manic Miner displays a dynamic title screen showing the sun setting behind an idyllic clifftop house, below which an animated keyboard plays pianola style the notes of a delightfully clangorous two channel rendition of The Beautiful Blue Danube by Johann Strauss.

Smith achieved this seemingly impossible feat by taking the idea of alternating sound fragments and silence to its logical extreme. By toggling the speaker on and off for a single clock cycle of the CPU, he could create a binary impulse – the shortest possible fragment of digital sound. By sequencing a series of these binary impulses one after the other at regular intervals it’s possible to create a pitched tone that’s more empty space than it is signal. By using two independent timers Smith was able to create the impression of two separate tones playing at the same time. The effect is rough and indistinct, but it hinted at what that simple speaker might be able to do.

In 1983, the software house Quicksilva released Ant Attack, a survival horror game. Like 3D Monster Maze on the ZX81, which introduced gamers to the first person perspective dino escape horror game, Ant Attack took the Spectrum into new and interesting graphical territory, bringing an isometric field of play and offering extra degrees of player control, creating a sense of agency and freedom of movement that was really quite innovative for the time. The use of monochrome shading, although a detail imposed by the Spectrum’s graphics hardware, contributes to the game’s look and feel, lending it something of the character of a 50s B feature, a thematic nod that continues through to its sequel, Zombie Zombie.

Developed by Sandy White and Angela Sutherland, Zombie Zombie draws on George A. Romero’s Living Dead series to create a dystopian cityscape in which the player has to lure zombies to precipices, so that they might fall to their death if indeed death is the right word to use here. Visually, Zombie Zombie is very similar to its predecessor, but its soundtrack is much more sophisticated. Building on the two channel routine of Manic Miner to create two completely independent tunable square wave tones from the Spectrum’s speaker.

Now getting the Spectrum even to play two channels was a phenomenal technical achievement, but a young programmer from St. Helens in the Northwest of England would take Spectrum music to a whole new level. In retrospect, Tim Follin’s earliest soundtracks showcase the incremental development of both his sound engine and his emerging musical style. The soundtrack for his first Spectrum game, Subterranean Stryker, is really interesting only insofar as it demonstrates some of his engine’s capabilities. It features a single channel melody line which drifts stylistically throughout, the programming equivalent of a guitarist noodling on a fretboard. Beneath the notes however, can be heard amplitude enveloping and a phasing effect creating a dynamically changing timbre, both features that Follin would continue to develop.

It was his third game, Vectron, a 3D maze game inspired by the Space Paranoids sequence from Disney’s Tron, where both the engine and Follin’s musical style really begin to shine through. The soundtrack in Vectron achieves three channels of playback, spitting out synth tones and a fast blues scale riff, not unlike the percussive organ lines of Keith Emerson and Rick Wakeman.

That love of Prog. Rock definitely shines through in Follin’s music, particularly in the soundtrack for Chronos a complex multichannel music track with percussion line and effects.

Follin’s engine works by using five of the Z80’s operators in a loop, all of which count down from a series of pre-determined values to zero. When each loop is complete, it generates a pulse wave whose width determines the speaker level. The constantly shifting pulse widths affect both the level and the timbre, adding noise, in the sense that the changing harmonic content introduces an undesirable roughness to the sound. It also causes tuning problems as the channel count rises.

That quality of sound though – that grungy fuzziness – came to define the sound of the Spectrum for a generation of gamers, becoming an important feature of the style in much the same way that the warmth of tape saturation came to characterise the sound of recorded music throughout the 1960s and 1970s. More than 35 years on from its launch and with over 24,000 software titles released, the ZX Spectrum remains one of the best-selling and most fondly loved machines in computing history, but it’s far from dead.

Back in 1982 Chapter 19 of the ZX Spectrum manual included a programme called Frere Gustav a few simple lines of BASIC that translated the melody of Mahler’s Funeral March, from his First Symphony into BEEP commands in Spectrum BASIC. The chapter ended with a challenge exercise. Program the computer so that it plays not only the Funeral March, but also the rest of Mahler’s First Symphony. Well, in 2014, Spectrum fan and retro-computing enthusiast, Matt Wescott, finally made good the challenge using a Raspberry Pi as the digital conductor to control an orchestra of 12 Spectrums at Geek Out, an event hosted at the Oxford Museum of the History of Science in 2014.

As the machines were networked and started their performance, Westcott’s heart was in his mouth. Nobody had any idea how it was going to turn out. The piece starts with one instrument playing two alternating notes in solo, before the other instruments join in. That solo seemed to last an eternity, but, when the second Spectrum joined in, Westcott’s sense of apprehension turned to relief, and he was able to relax and enjoy the music. The Spectrum then, even today, is a perfect counterpoint to the relentless drive of technological progress and the tyranny of choice that comes with it.

That simple sound and primitive technology forced developers to be creative, and in the process created a unique, characterful sound that is as much the sound of the 1980s as Godley & Creme or Depeche Mode. Next, I’d like you to follow the links below and download one of the ZX Spectrum emulators and a selection of public domain game ROMs. Play through the games and listen to the music. Can you identify from the sound, where in the developmental timeline the game is from? In a discussion group I’d like to hear your thoughts on the rapid development in complexity of ZX Spectrum soundtracks, and contrast that with the Atari VCS.

Why do you think that the Spectrum sound evolved while the VCS remained relatively fixed?