This is a tarana (called tillana in Carnatic), this is often an impromptu singing using words like ta dhoom.. tanana.. etc, one view is that these words have from tabla taalas but other view is that they are from jhala originating from sarod, sitar etc. AFAIK U Amir Khan has done a lot of work on this.I remember reading some where that U Bade G Ali Khan often did riyaz for hours and hours of palta, sargam, laykari watching waves of the sea with swaramandala in his hand, when you have riyazi gala like them you donnt have to think much while singing, they just remember structure of a raag say Hansdhavni , they know how it goes up and down, pakad , alaap and taan used, rest they can do impromptu.