Heartbeat SFX usually fail for two reasons: the tempo doesn't match the emotion, or the perspective doesn't match the camera. Use the prompts here as starting points, then adjust words that control rhythm feel (calm vs panic), filtering (muffled vs crisp), and space (dry vs roomy). A small change like "short decay" or "sub-heavy" can make the pulse either sit invisibly under dialogue or dominate the moment.
Match tempo to story beat (without naming a BPM)
Instead of chasing a specific BPM, describe the emotional state and pacing. "Calm and steady" reads very differently than "racing and anxious," even at similar speeds. If the edit is fast, ask for tighter spacing; if you need dread, ask for slower hits with a heavier tail.
- Use words like "steady," "racing," "stumbling," or "surging" to steer rhythm feel
- For tense pauses, request "slower with heavier thump" rather than just "loud"
- If it conflicts with dialogue, ask for "short decay" and "less room tone"
Choose a perspective: internal, close, or on-scene
A heartbeat can feel internal (heard in the head/body), captured by a device (stethoscope-like), or present in a room. Perspective is mostly filtering and space: internal tends to be muffled and low-mid focused; on-scene can carry reflections and air.
- Internal POV: prompt "muffled, filtered, warm thump, minimal highs"
- Device POV: prompt "stethoscope-style, narrow stereo, intimate and dry"
- Room POV: prompt "distant heartbeat, subtle reflections, quiet room tone"
Dial the low-end so it reads on any speaker
Too much sub can disappear on phones; too little can feel fake. Aim for a solid thump that's audible in the mids, then add or reduce low-end weight depending on the scene. If you want impact, request a stronger transient; if you want background tension, smooth it out.
- For phone-friendly: "audible mid thump, controlled sub"
- For cinematic weight: "sub-forward throb, strong low-end, wider stereo feel"
- To avoid clicks: "smooth attack, clean transient, no digital artifacts"
Make it loopable for longer tension beds
If your scene needs a continuous pulse, generate a loop-ready take and keep the edges clean. A loop works best when the tail is controlled and the ambience is consistent, so the seam doesn't jump out when repeated.
- Ask for "loopable, stable rhythm, smooth loop edges"
- Prefer consistent room tone over changing reflections for longer beds
- If the loop feels obvious, regenerate with "softer transient" and "shorter tail"
