How to write a backing track that fits a vocal you already recorded
Upload the unaccompanied vocal and tell Vizard Agent what style of backing you want. Vizard Agent measures the tempo, extracts the melody's pitches to find the key, calibrates a beat grid against the verses, then synthesises an arrangement to those chords and mixes it under the voice with sidechain ducking.
What do you type into Vizard Agent?
Say "synced to the vocal" rather than "add music". Vizard Agent treats the first as an instruction to analyse and arrange, and the second as an instruction to find something and lay it underneath, which are two different jobs with very different results. Name the style too, because it decides the instrumentation and the arrangement, not just the mood.
Prompt
What does Vizard Agent actually do?
A vocal sung without a click drifts in tempo, and no pre-made track will follow it. So the music is built to what the voice actually did, with the tempo, key and chord positions all derived from the recording before a single note is generated. In the session behind this article it:
- Measured the tempo, key and section timings with an audio analysis library, and used the word-level timings to treat sung verses and spoken sections separately.
- Calculated the verse lengths and aligned a beat grid to them, then calibrated it against the verse cue points and verified the beat counts in every section.
- Extracted the fundamental pitch and melodic notes from the singing, and analysed the energy profile and syllable onsets across the take.
- Generated and compared candidate backing tracks, checking each one's key and tempo against the vocal's.
- Calculated bar timings and chord progressions, synthesised the instruments and percussion, and mixed with sidechain ducking so the voice stayed present.
- Delivered a 1920x1080 video, 183.17 seconds at 30fps, with an animated waveform visualiser and karaoke captions.
When does this not work well?
Everything here is derived from the vocal recording, so its quality sets a hard ceiling. A wandering tempo is hard to grid, and heavy drift still resists calibration against the verses. Noisy recordings confuse pitch extraction, so a clean vocal gives a more reliable key. Synthesised instruments serve a song well but aren't a session band.
Common questions
Does the vocal need to be recorded to a click? No, and that is the point. Vizard Agent measures the tempo the singer actually used.
How does Vizard Agent find the key? It extracts the fundamental pitch and the melodic notes from the singing rather than inferring it from the genre.
Will the voice stay audible? Yes. Vizard Agent measures both stems and applies sidechain ducking so the backing drops under the voice.