Fenigstein, who is featured prominently among the singers cited in the Itzik Zhelonek collection, left very few traces. I was only ever able to find one picture of him, for instance, and it's not a very good one. There are a very few existing recordings. I always assumed he was one of the many singers and actors who died in the Holocaust but recently I heard from a researcher in Scotland who sent me this:
I'm a researcher at Glasgow university looking at Jewish music in Scotland in the early 20th century, and just discovering Herman Fenigstein. After leaving Warsaw (and a short spell in London), Fenigstein worked as a chazzan in Glasgow for several decades. Interestingly, he seems to have completely abandoned what seems to have been a successful Yiddish stage once here in Scotland.
He also sent me this obituary. You're welcome!