Voice input via Shift-V

who can point me to a place, where voice input is described?
I quite successfully wrote down a piece yesterday, where at some places I would have to input a second voice. I noticed: each time I used the Shift-V command, it would show an increased number. At the end I had already reached Voice #7.
How can I stay with Voice 2?

Shift-V always creates a new voice.

V (without shift) cycles through the voices that are created already.

thank you Rob, this explains it.