A self-proclaimed "Holocaust revisionist" mocked Anne Frank and Auschwitz survivors in songs described as "expressions of anti-Semetic hatred", a court heard.
Alison Chabloz, 53, faces five charges related to three songs which are "grossly offensive", the prosecution said.
A video of her performing a song entitled Survivors was applauded by her supporters in the public gallery at the opening of her trial at Westminster Magistrates' Court on Wednesday.
Chabloz, who carried two bunches of flowers into court before taking her seat in the dock appeared to mouth along to the lyrics of the song as it played.
Addressing the packed public gallery where people clapped at the end of the song, District Judge John Zani said anyone who repeated such behaviour would be ordered to leave the court.
On the video, Chabloz is heard in the footage to note the brackets symbol used in the name, something the prosecution said showed she was aware that it was often used as an anti-Semitic gesture known as an Echo.
The song devotes a verse to questioning the content of Anne Frank's diary and brands Nobel Prize winner and Holocaust survivor Elie Wiesel a liar.
Prosecutor Karen Robinson said: "The songs are designed to provoke maximum upset and discomfort.
"By the standards of an open and multi-racial society, they are grossly offensive."
A song entitled Nemo's Anti-Semitic Universe about what Chabloz described as an online troll has lyrics referring to notorious death camp Auschwitz as "a theme park just for fools".
Both songs were performed at a London Forum Event held at the Grosvenor Hotel in London in September 2016.
Of Chabloz's performances Stephen Silverman, director of investigations and enforcement at the Campaign Against Antisemitism (CAA) charity, said: "It is one of the most appalling expressions of anti-Semitic hatred I have ever seen."
Chabloz, of Glossop, Derbyshire, is represented by Adrian Davies, whose previous clients include controversial historian David Irving.
She denies two counts of sending by a public communications network an offensive, indecent or menacing message or material in relation to two of the three songs.
The defendant also denies two alternative counts of "causing" offensive material to be sent by a public communications network, after her performance was posted on her blog.
Chabloz, who accepted in a police interview being a "Holocaust revisionist", denies a fifth charge in relation to a third song entitled I Like The Story As It Is, which describes the Holocaust as a "damn fine tale".
This song, Ms Robinson said, was uploaded to YouTube by Chabloz.
The trial was adjourned until March 7, when the defence case will be heard.