Soundtrack: Vessel — Water music that assembles itself as you solve

Opening - sound seeping through a dim factory

A steampunk world where the inventor M. Arkwright has produced “Fluros,” labourers made of liquid. Boot up this liquid puzzle-platformer, covered in Komugi's review, and the first thing to reach you is a layer of soft-edged electronics. No showy melody announces itself; damp low end and pads seep into the factory dark. The tempo is roughly too slow to grab hold of, its beats rounded off by water. The weight of the sound sits nicely against the speed at which liquid crawls across the screen.

The music is by electronic musician Jon Hopkins, known for the albums he released on Domino. What makes Vessel interesting, though, is that he did not write fresh cues for it. What plays here is finished music Hopkins had already put out, taken apart and re-laid by audio director Leonard J. Paul's engine. That “artificial yet breathing” air in the first few steps is, you could say, a by-product of that dismantling.

It stacks as you solve - completion as the reward

The crux of Vessel's music design is that the thickness of the track is tied to your progress through the puzzle. When you first take up a mechanism, the sound is smooth, set gently far back in the mix. As you begin to grasp how to unpick it, drums and bass slot in and the sound grows more complex. And the instant the mechanism is fully solved, the full-length track rings out. The completion of the solution and the completion of the piece are laid on top of each other.

The person who made this possible is Leonard J. Paul. At GDC 2012 he gave a talk titled “The Dynamic Audio of Vessel,” describing how, on a foundation of FMOD, Lua and C++, he recomposed Hopkins's music dynamically using granular synthesis, subtractive synthesis, layered sequencing, spectral layering, LFO modulation - and “asymmetric loops.” The asymmetric loops are what made me sit up. Stack loops of unequal length and the seams become unpredictable; the same material never comes back wearing the same face twice. It loops, yet it does not sound like a loop.

So this music is not a short victory sting that fires when you win. While you are wrestling with a mechanism, you are, without noticing, stacking the track one sheet at a time. What plays the moment you solve it is not a reward dropped in from outside - it is the last piece of a track you have been assembling yourself.

Choosing not to compose fresh - the nerve to take finished tracks apart

One more thing worth noting is where the material itself comes from. Vessel uses seven tracks from Hopkins's 2009 album Insides (including the title track “Vessel”) and three from Contact Note - ten finished, already-released tracks in total. Nothing was recorded fresh for the game; records that were already on the shelf were brought in and unpicked into stems on the spot.

For a composer that is a fairly nervy choice. A finished track is usually blended into a single monolith. To be able to break it back into elements afterward and move them in and out with a puzzle's progress means the original was written with a structure that survives being taken apart. Hopkins's Insides-era sound keeps its layers - sustained pads, grainy electronics, rhythms that rise later - relatively distinct. That is exactly why Paul's engine could lay them out as scenery or push them to the front. It looks like the reuse of existing songs, but underneath sits the quiet condition that it only worked because the songs could be pulled apart.

The analogy to puzzling - solution and track resolve in the same order

I have a habit of measuring music in BPM, but putting a metronome to Vessel does not mean much. What corresponds here is not the speed of the beat but the order in which an image assembles. The solution to a liquid puzzle does not arrive all at once. Where to route a Fluro, which light to draw it toward - the fragments mesh in your head little by little, and finally click into an image. The track is exactly the same: it begins as a bed of pads, rhythm is inserted, and only with the final layer does the whole thing come into view.

So the pleasure at the moment of solving is doubled. The achievement of solving the puzzle and the achievement of completing the track overlap at the same instant. As Doremi I would put it this way: the music is standing in for the visualisation of progress. The player gauges how close they are not with the screen but with the ear. Not silence, not an endlessly looping bed, but a translation of the distance-to-solution into the thickness of sound - Vessel's music stands in that third position.

Tracks to hear - start with the title track

In-game the sound is dynamically dismantled, but the source material can be heard whole as Hopkins's official releases. Start with the title track from the album Insides, “Vessel” itself. Grainy piano and dusky electronics slowly shift in density - listening while you recall how that sound was laid down and pushed forward in-game, the pre-dismantled “monolith” comes into view, which is the fun of it.

Then the album the game drew from most, Insides itself. Its lead track “Light Through the Veins” takes nine minutes to resolve into an image, continuous with Vessel's philosophy of stacking (Jon Hopkins - Light Through The Veins (Official Audio) ↗). The official audio is available on the artist's Bandcamp and the streaming services, and on Steam alongside the game itself.

Closing - what I'd steal is “a structure that survives being taken apart”

If I were writing music myself, what I'd steal from Vessel is the design philosophy more than the technique. “Dynamic music” tends to pull the conversation toward implementation - preparing vertical stems - but what Vessel teaches sits one step earlier: write with dismantling in mind from the start, keeping the roles of the layers separate. A layer of sustained scenery, a layer of rhythm that rises partway, a layer that fixes the final image. Keep those three from fully blending and, even without an engine, you can move them in and out by hand later. Even already-released songs turned into dynamic music because they were written that way to begin with.

And the asymmetric loops. Overlapping loops of differing length to dissolve the seams works, well beyond games, whenever you write for waiting time or ambient settings. It is the cheapest way to keep the same material from growing stale. If you relisten, do it not as work background but while you are in the middle of solving something. Play this in the small hours before a deadline when your head isn't turning, and progress and the thickness of sound sync up in a strange way. To feel it together with the liquid physics, go from Komugi's review into the game. For other answers to dynamic music, I'll leave this column's COCOON and FRACT OSC pieces next to it.

Reference links

・Steam: Vessel (Strange Loop Games)

・Jon Hopkins official Bandcamp: Insides (includes the title track “Vessel”)

・Official audio (Provided to YouTube by Just Music): Jon Hopkins - Vessel

・GDC Vault: The Dynamic Audio of Vessel (Leonard J. Paul, GDC 2012)

・Designing Sound: Interview with Leonard J. Paul

・Wikipedia: Vessel (video game) (source for music and implementation techniques)