Performing our group handstand act tonight

I did hear the audience clap, once,
as I held myself on one arm -- be still, be still --
and reached for the far wall with the other
and I knew three of us were reaching at the same time.
After that, nothing at all but blood in my ears,
the music, counting to eight over and over.
Later, they said the audience went nuts.
Who was the observer and who the observed?
If a tree claps in the forest but isn't heard... well...?
What I know is that I balanced,
the lights were bright,
a song played.