What tempo should a lullaby prompt use?
Keep it between 60 and 70 BPM. This range matches a slow, steady rocking motion, which is why most lullabies sit there rather than at typical song tempos of 90 to 130 BPM. Going above 80 BPM tends to push the result toward a regular ballad rather than something sleep-focused.
Which instruments actually read as "lullaby"?
Music box, soft acoustic guitar, sustained piano and gentle strings all work reliably. Add humming as a vocal texture if you don't want full lyrics. Avoid naming drum kit parts like snare or hi-hats; if you want rhythm at all, say "light hand percussion" or "soft shaker" instead, since these read as gentle rather than a full beat.
How do I describe the voice for a lullaby?
Use "breathy", "soft" or "gentle female vocal" or "gentle male vocal". Our measurements on ACE-Step 1.5 confirmed that "whisper" reliably lowers loudness and "breathy" style descriptors move the vocal in a softer direction, so these are safe words to lean on rather than vaguer terms like "nice voice".
Should I write full lyrics or just ask for humming?
Either works. For an instrumental hum, say "instrumental" or "humming voice, no lyrics" clearly in the prompt so the model doesn't add unexpected words. For sung lyrics, keep lines short and simple, repeat a calming phrase in the chorus, and avoid complex rhyme schemes, since simple repeated lines suit a slow tempo better than dense verses.
How is a lullaby prompt different from a general acoustic prompt?
A general acoustic folk prompt (see our acoustic folk page) runs 70 to 125 BPM in open guitar keys like G major or D major. A lullaby prompt narrows that down: slower tempo (60-70 BPM), softer dynamics throughout, and no build-ups or loud choruses, since the goal is to stay calm from start to end rather than build energy.
Lyrics skeleton
Original, for structure
[Verse] Close your eyes, the day is done Stars are waking one by one [Chorus] Hush now, hush now, drift away Morning waits for another day [Verse] Moonlight rests upon your bed Soft dreams gather in your head [Outro] Sleep now, sleep now, all is well
Common mistakes
- Setting the tempo too fast (above 80 BPM): state a specific BPM such as 65 rather than leaving it to genre defaults.
- Mixing in energetic mood words like "uplifting" or "epic": stick to one consistent mood such as "soothing" or "calm".
- Naming full drum kit parts: use "light percussion" or "soft shaker" instead of "snare" or "hi-hats" to avoid a busier beat than intended.
- Forgetting to say "instrumental" when you don't want lyrics: without it the model may add sung words you didn't ask for.
- Writing long, wordy lyric lines: keep lines short (4-6 words) so they sit naturally over a slow tempo.