Steering neutral speech into emotion: prompt × LoRA-strength study

Can an intense steering prompt push a semantically neutral sentence into a target emotion on moss-tts-4.55b-voice-acting-v2 — and does the matching emotion LoRA (v3) amplify it? For all 40 emotions × 6 neutral sentences we compare five conditions — N0 neutral prompt / P steer-prompt / L50·L100·L150 steer-prompt + LoRA at 50/100/150% — best-of-6, scored with EmoNet (target-emotion strength), genuineness, vocal-burst blend and WER.

Key findings

The steering prompt alone lifts target-emotion strength by Δ0.006 on average over the neutral floor; adding the LoRA at 100% lifts it a further Δ0.047.
The LoRA increases the target emotion beyond the prompt for 25/40 emotions.
Dose–response: emotion strength rises 0.028→0.042→0.074→0.125 across 0/50/100/150% while mean WER moves 0.21→0.51 (over-drive cost).
Most LoRA-dependent (biggest Δ LoRA): Anger, Distress, Malevolence Malice, Impatience and Irritability, Amusement, Fatigue Exhaustion.
Achievable by prompt alone (big Δ prompt, little extra from LoRA): Concen.
Hardest to elicit even with LoRA (lowest best emotion): Sourness, Awe, Confusion, Doubt, Shame, Bitterness.
Cross-steering specificity: for 35% of emotions the intended emotion is the single strongest measured EmoNet dimension at L100.

Per-emotion strength: neutral vs prompt vs prompt+LoRA (sorted)

Dose–response & intelligibility cost

Prompt-only vs LoRA contribution

Expressive gain vs WER cost

Cross-steering specificity

All emotions (sorted by prompt+LoRA @100% strength)

emotion	N0	P	L50	L100	L150	ΔLoRA	WER@L100	best
Distress	0.00	0.04	0.13	0.27	0.29	+0.22	0.80	L50
Anger	0.01	0.02	0.08	0.26	0.33	+0.24	0.68	L50
Impatience and Irritability	0.05	0.06	0.09	0.21	0.31	+0.15	0.38	L100
Malevolence Malice	0.04	0.03	0.08	0.19	0.28	+0.16	0.57	L100
Interest	0.20	0.20	0.18	0.19	0.21	-0.01	0.23	L150
Fatigue Exhaustion	0.05	0.08	0.13	0.18	0.24	+0.10	0.52	L150
Fear	0.02	0.05	0.10	0.13	0.22	+0.08	0.51	L100
Amusement	0.03	0.01	0.02	0.13	0.16	+0.11	0.60	L150
Helplessness	-0.00	0.04	0.11	0.12	0.25	+0.08	0.55	L100
Emotional Numbness	0.05	0.06	0.11	0.12	0.29	+0.05	0.68	L50
Sadness	0.00	0.04	0.04	0.11	0.26	+0.07	0.31	L150
Pain	0.01	0.02	0.04	0.10	0.27	+0.08	0.63	L50
Sexual Lust	0.01	0.02	0.08	0.10	0.17	+0.08	0.31	L150
Hope Enthusiasm Optimism	0.06	0.02	0.01	0.09	0.17	+0.07	0.44	L150
Longing	0.03	0.07	0.07	0.08	0.15	+0.01	0.23	L150
Intoxication Altered States of Consciousness	-0.00	-0.00	-0.00	0.08	0.23	+0.08	0.50	L100
Relief	0.02	0.02	0.03	0.08	0.07	+0.05	0.19	L100
Triumph	0.01	-0.00	-0.00	0.07	0.18	+0.07	0.55	L100
Concentration	0.05	0.11	0.07	0.06	0.05	-0.05	0.29	P
Astonishment Surprise	0.00	0.02	0.02	0.05	0.15	+0.04	0.28	L150
Contempt	0.03	0.00	0.02	0.04	0.08	+0.04	0.43	L100
Affection	0.02	0.04	0.05	0.04	0.05	-0.01	0.49	L50
Disappointment	0.00	0.00	0.03	0.03	0.05	+0.03	0.33	L150
Disgust	0.00	0.00	0.00	0.03	0.09	+0.03	0.42	L150
Contemplation	0.00	0.02	0.03	0.03	0.04	+0.01	0.31	L150
Thankfulness Gratitude	0.01	0.03	0.02	0.03	0.02	-0.00	0.21	P
Embarrassment	-0.00	0.01	0.00	0.02	0.03	+0.02	0.10	L150
Contentment	0.00	0.02	0.06	0.02	0.02	+0.00	0.13	L50
Pleasure Ecstasy	0.03	0.00	0.02	0.02	0.04	+0.02	0.26	L150
Elation	0.00	0.01	0.00	0.02	0.08	+0.01	0.38	L150
Jealousy and Envy	0.01	0.01	0.02	0.01	0.01	+0.00	0.21	L50
Sourness	0.00	0.00	0.00	0.01	0.01	+0.01	0.26	L100
Teasing	0.06	0.02	0.02	0.01	0.10	-0.01	0.13	L150
Infatuation	0.03	0.01	0.03	0.01	0.03	+0.00	0.14	L50
Pride	0.03	0.00	0.00	0.01	0.02	+0.01	0.25	L150
Confusion	-0.00	0.00	0.00	0.01	0.01	+0.01	0.37	L150
Shame	0.00	0.00	0.01	0.01	0.00	+0.00	0.27	L100
Doubt	0.00	0.01	0.01	0.01	0.01	-0.00	0.45	L150
Bitterness	0.00	0.00	0.00	0.00	0.00	+0.00	0.29	L150
Awe	0.00	0.01	0.01	0.00	0.00	-0.01	0.24	P