Dwitala avadhanam refers to putting two different talams simultaneously with both the hands for one song.
and more about this can be found at http://ramsabode.wordpress.com/2010/06/
See under Lec Dem – Dwitala Avadhanam
Here are two songs by Smt. Suguna Purushothaman providing Dwitala Avadhanam.
http://www.youtube.com/watch?v=DKL7Ko3JZjE 'E'-SWARA-001-Smt. Suguna Purushothaman-Natanamatinar-Vasantha
http://www.youtube.com/watch?v=DJaf-aTDe_0 E'-SWARA-002-Suguna Purushothaman-Kanna karuneela vanna-ragamalika.
venkatakailasam