She surely did. Sadly she didn’t remain with them for long. Grace was awesome too. This doesn’t do it justice, but if you can buy this song or album and listen carefully to this vocal power.
https://www.youtube.com/watch?v=sHEh7nNlTTI
https://www.youtube.com/watch?v=QC8K_jV38WU
Here’s a really good quality recording of a JA concert at the Filmore from Sept. 30, 1966 - 15 days before Signes last concert with them.
I had Surrealistic Pillow on cassette back in college (late 70’s). I’ve been on a JA kick for a few days now! Great music.
There are some radio interviews of Signe that are interesting where she talks about the band, leaving, no regrets, etc.