I call this "hands busy heart open", one of the many things I do as a doula. Applying counterpressure during surges, and when they ease I am resting with mama, watching without looking, waiting with confidence. I may use the quiet time to check on the birth pool, to communicate with others in the room if necessary.
It becomes a rhythm, and you get to feel with her when the next one is coming. One of my fondest memories from a birth is us all, myself, mother and father dozing on the sofa between surges, then getting swiftly back to action when another one came!
As labour progresses you'll usually find me sat on the birthing ball at the side of the pool - sometimes still giving counterpressure (something I did once leaning over the pool while heavily pregnant myself!), holding gas and air, stroking the hair back from mama's face.
There is always a moment when she begins to bear down and the familiar noise brings a smile to my face. The father looks at me - "is this still okay?" his eyes are saying, taken aback by the strength of the sound that he was told would come, yet in the moment it seems more powerful and primal than he could have imagined.
"Yes" my smile replies "yes things are unfolding perfectly"
Photograph of myself as doula at an incredible home birth, shared with kind permission