The braam is the most recognisable sound in modern film marketing: a distorted brass blast over an enormous sub, placed on a cut and decaying for several seconds. Good ones are hard to buy, because the library versions have already been used by everyone else. A generated braam is yours alone, and you can render a version with a longer tail when the edit changes.
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.
enormous distorted brass braam, low blaring horn blast with a huge sub underneath and a long decaying tail
two braam hits in succession, distorted brass blasts a beat apart with overlapping sub tails, enormous space
tension building for three seconds then landing on a massive distorted brass braam with a long tail
pure cinematic sub bass drop with no midrange, deep pitch falling and sustaining, felt more than heard
trailer impact with a bright metallic transient over a deep distorted boom, long shimmering decay
hybrid trailer hit blending a dark male choir with distorted brass and a sub drop, cathedral scale
huge percussive trailer boom, gated drum-like impact with a compressed room and a fast tight decay
reversed swell sucking backwards for two seconds then landing on a massive distorted trailer impact
short sharp trailer stinger, aggressive distorted stab with almost no tail, dry and violent
final trailer hit, enormous impact with a twelve second decaying tail settling into a low drone
These models respond to physical description. Name the material, the action and the space.
enormous distorted brass braam, low blaring horn blast with a huge sub underneath and a long decaying tail
Name all three components (brass, sub, tail). A braam missing any one of them becomes a different sound.
huge percussive trailer boom, gated drum-like impact with a compressed room and a fast tight decay
"Gated" and "compressed room" describe the production treatment, and these models respond well to that vocabulary.
pure cinematic sub bass drop with no midrange, deep pitch falling and sustaining, felt more than heard
"No midrange" keeps the sub out of the way of everything else, so you can stack it under an existing hit.
final trailer hit, enormous impact with a twelve second decaying tail settling into a low drone
The last hit of a trailer is defined by its tail. A tail that long needs a render length to match, or it gets cut off.
Brass gives the identity, the sub gives the physical weight, and the tail gives the scale. Without brass you get a generic boom; without the sub, a horn; without the tail, something that sounds small however loud it is. You can prompt all three together, or generate them separately and stack them, which is useful when you want the brass from one take and the weight from another.
As with bells, the decay tells the audience how big the space is, and trailer hits are built to sound like they happen somewhere the size of a canyon. So give the render enough seconds. A braam with a six-second tail rendered into a three-second clip loses its scale, and adding reverb afterwards does not convincingly restore it.
Trailer hits land through contrast: near-silence before, and space for the tail to decay into afterwards. That is an edit decision, but it changes what you should generate: a hit with a clean start and a long uninterrupted decay, without padding of atmosphere. Ask for a dry start and a long tail, and leave the silence to the timeline.
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}'