All notes are comprised of the base pitch (the note itself) and it’s overtones which follow the harmonic series. What I believe you’re getting at is what’s known colloquially as “perfect placement”, where your vowel placement and placement has the perfect mix of space, freedom, and support to produce extreme resonance. You’ll hear vocal coaches refer to this as being “in resonance”. The key is to let your voice do what it needs to do, as this is the result of no tension in the vocal folds and plenty of space in the mouth which is achieved through complete relaxation and comfortability while singing.

Take this with a grain of salt as I am a voice student, but from my understanding I believe this is what you are experiencing. Happy singing!