By Prithwish Ganguly

MUMBAI (Reuters) - For composer A. R. Rahman, the biggest challenge in "Jodhaa Akbar" was creating music that could echo the union of cultures in the period film -- the story of 16th century Mughal emperor Akbar's romance with a Rajput princess.

"Story wise it is about two cultures coming together in a love story," said Rahman. "It was a big challenge for me to compose music keeping in mind this theme of union."

Known for his musical versatility -- from romantic compositions to foot-tapping numbers -- Rahman has innovated with different instruments and sounds to create some of India's best known musical hits for more than a decade.

But for filmmaker Ashutosh Gowariker's ambitious project, the Bollywood composer said he had kept the modern day audience in mind.

"The sounds and songs are very contemporary," said Rahman. "It is a period film but I have not gone into using Rudraveena or those classical instruments while composing."

"The music is simple - mainly instruments and vocals and there's no flashy use of sounds."