NOW THEY'VE all been here, all the young lady folk singers who are making such heavy box office reputations for themselves. We've had Joan Baez and Judy Collins and Buffy St. Marie and this weekend we had Joni Mitchell at the University of California.

Miss Mitchell is a Veronica Lake blonde with a little-girl-blue costume and a guitar. She writes first class songs (one night last week I heard first Pete Seeger on the Merv Griffin show and then Glenn Campbell sing her hit "Both Sides Now") which are all in great demand by the pop-folk performers. And justly so; they are well constructed songs with poetic imagery that is consistently graphic and effective.

As a performer she has a good voice, through she is uncertain in her a capella numbers and has a strange style of phrasing rhythmically which was especially evident in her version of Dino Valente's "Let's Get Together" which she unsuccessfully tried to make into a sing-along.

She stays in one place, however, with her style and her songs and one could wish she would abandon her gingerbread-and-popsicle palace to tell us where she's really at.

The Lamb, which opened the concert, was pretentious, tedious and a bore. Their standing ovation merely removed all value from the act.