Brightness is not loudness
Many singers lift the chin, press the throat, or get louder to sound brighter. It may change the sound briefly, but often adds tension. Find an easy bright point first.
Use vowels to check resonance
On the same pitch, switch gently between vowels and notice which one clears up most easily. Then transfer that sensation into words.
Stable breath supports stable tone
If airflow changes unpredictably, tone can become dark, weak, or squeezed. Resonance work pairs well with breath stability.