My first tête-à-tête with Sadaraa was when I heard Purbayan Chatterjee presenting vocal during his Sitar recital of Raag Kedar .. "जागे कौन महल में सोया रे" (jaage kaun mahal mein soya re ). Subsequently I realized that I had heard many bandishes in Dhrupad and Khyaal style renditions , that were basically to labelled as "Sadraa". The most popular of such Sadraas is the Bhairavi by Begum Parveen Sultana "Bhavani Dayani" ( भवानी दयानी ).
Sadaraa , Sadara or Sadra (सदरा) is a form of Indian Classical Vocal genre , that connects Dhrupad style to that of Khyaal. The characteristic feature of Sadra is that, it is always composed in a ten (10) beat cycle taal such as Jhaptaal.
A single line or sentence is repeated (similar to Dhrupad), decorated with meend , gamaks and bolbaat taans. In addition , it has decorative tools of murkis and taankaari that is typically characteristic of Khyaal genre. One important characteristic of Sadraa is that the bols or lyrics have a blend of devotion , spiritualism and deeper philosophy.
Here Pt Ajoy Chakraborty sings the Sadraa in Kedar ( starting 34.10 )
Jage kaun Mahal me soya.
The quintessential Bhavani Dayani by Begum Parveen Sultana
Bhavani Dayani of Pt Ajoy Chakraborty
Reference
Sadra (music) on wiki
Musings - Pondering and other stuff
Dhrupad-Khyaal Sanvaad
Khyaal (ख्याल)