A drone is the least noticeable element in a soundtrack and one of the most important. It sets what a scene feels like before anything happens, and it holds a long take together when nothing else does. A good drone moves slowly enough not to draw attention, but enough that the ear keeps hearing it, and you can control that balance from the prompt.
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.
dark sustained drone, low detuned tones slowly beating against each other, oppressive and airless, seamless loop
spacecraft interior drone, warm low mechanical hum with a faint high electrical shimmer, seamless loop
vast sustained drone suggesting enormous scale, slow swelling low strings and choir under a hall of air, seamless loop
industrial drone with a slow rhythmic throb, distant machinery pressure and metallic resonance, seamless loop
tension drone slowly rising in pitch and density over twelve seconds without ever resolving, dissonant
deep underwater drone, immense low pressure with distant groaning hull creaks, submerged, seamless loop
sparse arid drone, thin high shimmering tone over a warm low bed with occasional distant wind, seamless loop
electrical drone with an unstable mains hum, buzzing and intermittently flickering, close and claustrophobic
ethereal choral drone, wordless voices sustaining a slowly shifting consonant chord, huge reverberant space
pure low frequency rumble bed with no midrange or top, slowly undulating, felt more than heard, seamless loop
These models respond to physical description. Name the material, the action and the space.
dark sustained drone, low detuned tones slowly beating against each other, oppressive and airless, seamless loop
Detuned tones beating against each other create unease: a dissonance you feel as movement more than hear as a chord.
vast sustained drone suggesting enormous scale, slow swelling low strings and choir under a hall of air, seamless loop
Dread and awe differ in consonance and space. The technique is the same, with the opposite harmonic instruction.
tension drone slowly rising in pitch and density over twelve seconds without ever resolving, dissonant
"Without ever resolving" keeps it a bed instead of a riser. It moves but never arrives, so it does not pull focus.
pure low frequency rumble bed with no midrange or top, slowly undulating, felt more than heard, seamless loop
A sub-only bed can sit under dialogue without masking any words, which makes it the most reusable drone in a library.
A perfectly static tone fades from perception within about twenty seconds as the ear adapts. A drone that undulates, beats or drifts slowly stays present without becoming an event. Ask for the movement: "slowly beating", "undulating", "slowly shifting". Without it, the audience stops hearing the bed partway through the scene.
Drones usually fail in the mix, and the cause is almost always that they share the midrange with the voices above them. A sub-only bed, or one with its energy high and airy, can sit loud without masking anything. Prompt the band directly ("no midrange", "thin high shimmering tone", "low pressure"). That works better than EQ afterwards, because the model produces a sound made for that register.
These render up to two minutes at a time, which is often long enough that a scene needs no loop, and an unlooped bed has no loop point to give away. When you do need a loop, ask for a seamless loop and keep the request steady, because a drone that swells inside its own clip cannot join to itself. Then cut at a zero crossing in the quietest moment, which for a drone takes seconds.
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}'