Emotional Arc
Does the song move from state A to state B? Revelation, release, recalibration. Not just emotion, but emotional motion.
What good looks like
The listener ends the song in a different place than they started. Something shifted.
How SongForgeAI scores it
emotional-arc.ts (Build 945) classifies arc shape as flat / single-axis / shaped / volatile using per-section valence + arousal delta. "Flat" is a wound; "shaped" is the target.
Example score
75/100on this metricV1 grief (valence -0.4) → bridge contemplation (-0.2) → final chorus exhaustion (-0.6)
WhyArc is shaped, not flat — the song moves. Would score higher with more delta on the final chorus; the speaker ends in roughly the same emotional weather she started in. The progression earns points; the landing leaves them on the table.
One representative example. Real scores carry a reproducibility seal — verify at /scoring/standard.
Common failure mode
Static emotional weather — the song is sad in verse 1 and sad in the chorus and sad at the end. No motion, no release.
What it looks like in the wild
- Verse 1 grief → bridge recontextualization → final chorus reframed.
- A song that starts at 7/10 intensity, dips to 3 on the bridge, and lands at 9.
- An ending that the beginning wouldn't have predicted.
Why it’s in the Impact tier
Will anyone remember it tomorrow? Transcendence, arc, stickiness, and genre fit.
The Impact tier contributes 35% to the final composite score. The tier weight is distributed across its member metrics — no single metric dominates the composite.
Other Impact metrics
The Transcendent Line
#9The unrepeatable line. Not necessarily the cleverest; the truest. The line someone would quote.
Memorability
#11The one-hour test: could you recall this 60 minutes after hearing it once? Hooks, refrains, and sticky phrases.
Genre Authenticity
#12Does this honor its genre while extending it? Genre fluency without genre cliché.
The full rubric
Related reading
How to Write a Bridge That Actually Changes the Song
Narrative Arc usually fails at the bridge — the test of whether the song goes anywhere.
Read the guidePublishing the Lyric Scoring Standard v1.0
The rubric itself, open-sourced under CC BY 4.0.
Read the essayWhy the default score is 50, not 75
Why the Gravity Rule keeps every metric honest.
Read the essayAnatomy of a Forge: one song from prompt to final score
See this metric scored on a real forge run, alongside all 11 others.
Read the essaySee this metric scored against real songs
Every song forged through SongForgeAI is scored on Arc. Browse the leaderboard or forge your own to see how lines land on this axis.