Could this be Florence?
From SF Gate Thursday, March 6, 1997 (I assume this is San Fancisco.)
Florence Welch Bruce, a supporter of the San Francisco Opera since the 1930s and the creator of the Florence Bruce scholarship for promising musicians, died February 24 in her Hillsborough home after a brief illness. She was 90.
A native of San Francisco and a graduate of the Katherine Burke and Hamlin schools in San Francisco, Mrs. Burke was active in the Red Cross during World War II.
She was a past president of the San Francisco Opera Guild and helped develop the opera's Merola Fund.
She was a supporter and volunteer at the San Francisco and San Mateo arboretums and was a former member of the board of Mills Hospital.
Her husband of 45 years, Starr Bruce, died in 1969.
There is a marriage of a Starr Bruce to a Florence Elaine Welch on 11 November 1926 in San Francisco, California. Her parents are given as Andrew Welch and Julia De Laveaga.
It doesn't state that she was a mezzo soprano but it could be her. But it may not as she was 90 in 1997 so born 1907. If she was recording in 1911 then I think four years old would be too young!!
I assume you have no idea where she could have been born. Of course Florence Bruce may have been a stage name and not her real name! Interesting that nothing seems to come up on Google that is of any significance.
