A riser is built around its ending. The rate it climbs, the way it thins out at the top and the silence it leaves all serve the cut it lands on. That is why library risers are frustrating: you get a four-second build for a three-second gap and no clean way to fix it. Generating one at the exact length you need is the clearest case in this library for making a sound instead of searching for one.
Every clip shows the exact prompt that produced it. The render script reads its prompts from the same file as this page. Copy one, change a word and generate your own.
white noise riser building steadily in volume and brightness over four seconds and cutting off sharply, wide stereo
tonal riser, synthetic pitch climbing steadily upward with growing intensity, ending abruptly, wide stereo
metallic riser built from scraping metal harmonics accelerating upward into a hard stop, harsh and wide
orchestral string section building from soft tremolo to a full dissonant fortissimo, large hall, ending on a cut
shepard tone riser, layered octaves creating an endlessly rising illusion, smooth and unsettling, seamless loop
percussive riser, drum hits accelerating from slow to a blur over six seconds then stopping dead, big room
choir swelling from a whisper to a full dissonant cluster over eight seconds, cathedral reverb
downlifter, pitch and energy falling away steadily into a low settled hum, wide stereo, cinematic
digital riser built from stuttering glitch artefacts accelerating and rising in pitch, harsh, ending abruptly
very long cinematic riser building slowly over twelve seconds through noise, tone and low rumble to a hard cut
These models respond to physical description. Name the material, the action and the space.
white noise riser building steadily in volume and brightness over four seconds and cutting off sharply, wide stereo
Put the length in the prompt and set the render to the same number so it lands. "Cutting off sharply" gives you a clean edit point.
tonal riser, synthetic pitch climbing steadily upward with growing intensity, ending abruptly, wide stereo
Tonal risers sit in the harmony and can clash with music; noise risers sit outside it. Choose on purpose to avoid a fight in the mix.
shepard tone riser, layered octaves creating an endlessly rising illusion, smooth and unsettling, seamless loop
The Shepard tone is a named illusion the models know. Asking for it by name is more reliable than describing the effect.
downlifter, pitch and energy falling away steadily into a low settled hum, wide stereo, cinematic
Downlifters cover the other half of a transition. You usually want a matched pair, and generating both in one session keeps them related.
A build that is even a quarter second too long has to be trimmed from the front, which removes the quiet beginning that made it feel long. One that is too short has to be stretched, which smears the top. Measure the gap in your timeline, set the render to that number, and say the number in the prompt as well. The round trip takes about fifteen seconds.
Risers end in one of three ways: a hard cut into silence, a cut into an impact, or a spill of reverb that carries over the edit. The first is tense, the second violent, the third a reveal, and they are not interchangeable. Say which you want ("ending abruptly", "cutting off sharply", "spilling into a long reverb tail"). If you do not, the model tends to fade out, and a fade rarely works.
A big trailer build is usually three risers at once: noise for the top, a tonal element for the middle, and a low rumble for the weight. Generating them separately and stacking them lets you time each one and keeps the mix controllable. That is why this collection has a noise riser, a tonal riser and a long combined build instead of ten variations of one sound.
The models run on your machine, which changes the cost, the privacy and what you can automate.
Weights are fetched once. After that, generation, the library and the API all work with the network off. Everything lives in one SQLite file and one folder of WAVs under ~/.soundbox, and nothing is uploaded.
Soundbox runs an MCP server in the same process, with tools for generating and listing sounds. Generated files come back as absolute paths, so an agent can copy them into a project.
Every model's terms are shown before you download it, and non-commercial weights need an explicit confirmation. Soundbox is MIT. The licence of the model that made a sound governs what you may do with it.
claude mcp add --transport http soundbox http://127.0.0.1:17494/mcpcurl -X POST http://127.0.0.1:17494/api/generate \
-H 'Content-Type: application/json' \
-d '{"model":"audiocpp-stable-audio-3-sfx","prompt":"8-bit coin pickup blip","duration_s":1}'