Special Judge Poonam Chaudhry asked the counsel for Mr Dinakaran and Sukesh Chandrashekar to file their replies on May 15.
Delhi Police's Crime Branch submitted before the court that they needed the voice samples for their probe into the Rs 50-crore graft case.
It said they had a CD containing audio recordings of phone conversations between Mr Dinakaran and Mr Chandrashekar and others, and they wanted to compare the audios with the voice samples.
After the counsel for the two accused sought time to go through the application, the court listed it for May 15.
Mr Dinakaran and Mr Chandrashekar were also brought to the court from judicial custody in pursuance to its production warrants issued earlier.
Meanwhile, the court also extended till Monday Mr Chandrashekar's judicial custody, which would have expired tomorrow.
Mr Dinakaran was arrested here on the night of April 25 after four days of questioning for allegedly attempting to bribe an unidentified Election Commission official to get the undivided AIADMK's 'two leaves' election symbol. His faction hoped to obtain the symbol for a by-election to the RK Nagar Assembly seat in Tamil Nadu, which was later cancelled by the Election Commission (EC).
The EC had frozen the AIADMK's symbol after two factions of the party -- one led by Mr Dinakaran's aunt Sasikala and the other by former Chief Minister O Panneerselvam -- staked a claim to it.
Mr Dinakaran has been accused of allegedly arranging the amount from undisclosed sources and getting it transferred from Chennai to Delhi through illegal channels.
Mallikarjuna was arrested for allegedly facilitating the Rs 50-crore deal between Mr Dinakaran and Mr Chandrashekar, who was arrested on April 16.
Singh was held on the night of April 27 with the police claiming that he was given Rs 1 crore to hand over to Mr Chandrashekar. The money was meant to be paid as a bribe to someone in the Election Commission, the police had told the court.
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.