Herz-Sommer died in London Sunday with her family at her bedside, Ariel Sommer, told CNN.
"Much has been written about her, but to those of us who knew her best she was our dear 'Gigi,' Sommer said. "She loved us, laughed with us and cherished music with us. She was an inspiration and our world will be significantly poorer without her by our side."
Herz-Sommer, originally from Prague, was locked up at the Theresienstadt concentration camp during World War II.
The talented musician and pianist performed concerts with other inmates that entertained their Nazi captors.
"My world is music. I'm not interested in doing anything else," she said in a 2014 Academy Award-nominated documentary, "The Lady in Number 6: Music Saved My Life."
"I knew that we will play," Herz-Sommer said in the documentary. "And I was thinking when we can play it can't be so terrible. The music, the music! The music is the first place of art. It brings us on an island with peace, beauty and love."
Herz-Sommer was living in Prague when she and her 5-year-old son, Raphael, received deportation orders from the Nazis and were sent to Theresienstadt, the documentary's website said.
Herz-Sommer performed in more than 100 concerts in the camp and tried to protect her son physically and emotionally, the documentary's website said.
As an adult, Raphael, who was an accomplished cellist, said he had few dark memories of Theresienstadt, once writing his mother managed to create a Garden of Eden for him in the midst of the ordeal.
Herz-Sommer and her son returned to Prague after they were freed by the Soviet Army in May 1945, the documentary's website said. She eventually settled in London.
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