Music composer brothers Salim and Sulaiman Merchant have spent the past two decades providing the soundtracks and songs to some of Bollywood's biggest films, including Band Baaja Baaraat (2010), Rab Ne Bana Di Jodi (2008) and Aaja Nachle (2007).

Known as Salim Sulaiman, they are widely recognised as prolific music directors, with Salim, 42, taking on keyboard and vocal duties and Sulaiman, 45, helming percussion and drum programming.

So what are the Manganiyars, folk singers from Rajasthan, doing at their concert on Saturday at The Star Theatre?

Speaking to The Straits Times from Delhi, India, Salim says this came about after the brothers attended a private concert hosted by the prince of Udaipur in February.

"We heard these amazing folk singers called the Manganiyars from Rajasthan at the concert and I knew immediately that our sound for 2016 was going to be a fusion of Bollywood and folk."

Among the voices, one stood out for him. It turned out to be that of Sattar Khan, whom Salim had run into as a judge on Season 5 of Indian Idol in 2009. At the end of Khan's audition, Salim was so moved by the then-16-year-old's soulful performance that he lifted him up in his arms and embraced him - a scene that has resurfaced for the promotional clips for their concert.

Khan will be part of the Manganiyar troupe performing with the brothers in Singapore as part of a tour that has already travelled to the United States and Canada. This will be Salim Sulaiman's second performance here, after their 2013 concert at the Esplanade.

The foray into folk music fits right into what the brothers have been doing in the past few years, focusing on more personal projects and ticking off their bucket list.

"When you're a Bollywood composer working in the main film industry, there's lots of pressure and you don't have time to do anything else. As human beings and as artists, we also have to satisfy our own artistic needs," says Salim.

Hence the duo have been involved in everything from a West End musical production called Beyond Bollywood last year to chronicling their music journey in a documentary called Shukranallah, which was released via iTunes this year. And their film of choice this year is Poorna, a biopic about the youngest girl to climb Mount Everest.

Long-time fans of the duo need not worry though, as they have not left the Bollywood hits off the setlist. Their show will also feature playback singers such as Aditi Sharma, Raj Pandit and Vipul Mehta.

"Apart from our big blockbuster songs, we have these beautiful collaborations with the Manganiyars, where we've basically fused folk songs into some of our big hits, like O Re Piya from Aaja Nachle and Yeh Honsla from Dor," he says.

The show will also feature Qawwali - a form of Sufi devotional music - and a retro throwback section paying tribute to music by the likes of acclaimed film composer R. D. Burman.

"My heart is in a different place and very connected to my devotional and traditional side at the moment, so I'm going to live it as much as I can till I get bored of it," says Salim.

After all, as he puts it: "I can always jump back on the Bollywood bandwagon."