The voice samples of BJP Wayanad district secretary Prashant Malavayil were taken earlier.
Voices of both Surendran and Janadhipathya Rashtreeya Party leader Praseetha need to be examined, a court ruled on Friday while considering the case.
Janu claimed that she had no clue about the money deals alleged to have taken place between Surendran and JRP leader Praseetha until news about it came to light.
The FIR was filed under Sections 171 E (bribery) and 171 F (Punishment for undue influence or personation at an election).
Earlier on Wednesday, JRP treasurer alleged that Janu had demanded Rs 10 crore, five Assembly seats for JRP, and the post of a Union minister from BJP.
CK Janu had unsuccessfully contested the Assembly polls as an NDA candidate from Sulthan Bathery in Wayanad.
Kerala has been watching Janu’s political moves seriously after she led the historical Adivasi land agitation movement, under the banner of Adivasi Gothra Maha Sabha.
She has completed a major portion of the book titled Adimasanthathiyude Adayalappeduthalukal or Recordings of a Slave’s Ward, which appears to be a new subaltern chapter in Malabar history.