I went last night to a Prom concert.  Bruch's violin concerto was played by  young Norwegian with the fine lupine name of Vilde Frang (having a half-Norwegian daughter entitles me to comment).  She was mightily impressive.        I was in the seats behind the orchestra, and as I watched her frizzed mane of hair vibrating to the music I     wondered how many of the younger breed of soloists, or just outstanding players, are women, and how far this varies by instrument.  Only one of the orchestra's double basses was a woman, for obvious reasons, and none of the percussionists.  For most of the strings, it was 50/50ish.   Whatever the…