The old adage of advertising used to be: if you have no other ideas, show a baby. When it comes to film promos in India, make that patriotism.

The makers of Rajkahini, national-award-winning director Srijit Mukherjee’s Bengali film set during the freedom movement, have tapped this vein to create what may well become that elusive creature: a promo that goes viral. Interspersed with clips from the film, the video makes clever use of India’s national anthem.

To understand, listen to this.

Chances are, after the 1:16 mark, where Pandit Jasraj gives the finishing sur to the first stanza, we will run into unfamiliar territory. This video shows how rarely the song which the national anthem is part of is sung in its entirety.

Picking up on the same idea, the Rajkahini promo features only the other five stanzas of the hymn, leaving out the one we’re familiar with.

Titled Bharoto Bhagyo Bidhata , the video is a minor coup in terms of its assemblage of almost every popular contemporary singer in Bengali, cutting across genres. Starting with the self-styled minstrel of songs of the soul, Kabir Suman, the line-up comprises Kaushiki Chakraborty, Rupankar Bagchi, Lopamudra Mitra, Rupam Islam, Babul Supriyo, Sraboni Sen, Siddharta Sankar Roy, Srikanto Acharya, Anupam Roy, Annwesha, and Indraadip Das Gupta.

In other words, Indian classical, rock, pop, film-music and Rabindrasangeet are all represented. Despite this – and in spite of the clever use of harmonies – there is a certain sameness in the delivery that does not bring out the uniqueness of style and genre that the singers are capable of. The outcome is rousing, but not intricate in its rendition.

Still, this video will probably spread the word out about the film – featuring an ensemble cast that includes Rituparna Sengupta, Saswata Chatterjee, and Abir Chatterjee – quite effectively before its October 16 release.