The 66-year-old is charged with insulting President Islam Karimov and threatening public security.
Human rights activists say the real reason behind his trial is Hasan's song about last year's bloody events in Andijon.
Hasan's public defender Surat Ikramov, who also heads the Initiative Group of Independent Rights Defenders, told RFE/RL's Uzbek Service that the judges and prosecutors could not agree on whether to let independent observers be present in the courtroom.
Ikramov said supporters, human rights activists, and diplomats were not let in, but reported that the judges "said they would let them in next time."
The trial was adjourned until August 9.