I am sitting on the sea wall outside the National Centre for Performing Arts (NCPA) at the end of Mumbai's magnificent Marine Drive, enjoying the view of the Arabian Sea and the warm, muggy breeze that continuously feeds this vast city.

I am offered roasted sweet corn, a cup of sweet chai and the chance to see a monkey dance to the beat of a small drum. A policeman blows his whistle, insisting that a carefree group of young Mumbaikers - enjoying the seashore between the monsoon downpours - clamber back up the huge breakwater away from the brown water...

I have just finished rehearsing at the NCPA with 230 children from across all strata of Mumbai society.

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The extreme contrasts of modern India are laid bare at the stage door: some children are picked up by chauffeured Mercedes, while others patiently wait for a municipal bus that will return them to an NGO-run school in one of the city's many slum areas.

The choral concert I am to conduct marks the culmination of two months spent in India's most populous, energetic and contradictory city, rehearsing weekly with eight separate choirs. As the concert nears and all the young singers come together on the NCPA stage, all the differences of privilege, schooling, religion and language are quickly forgotten.

The final bars of Going For Gold, a sports cantata written by Edinburgh-based composer Tom Cunningham, ring in my ears as I watch the youngsters head home.

Composed for the National Youth Choirs of Scotland, the sentiments of this jovial and melodic piece have gone down well with the Scots' sporty Indian contemporaries: "Faster, Higher, Stronger; fortune favours the bold", they sing heartily. "No pain, no gain, if you want to be a champion… you've got to do the work to win the ultimate prize."

Equally popular are settings by Howard Blake (he of The Snowman fame) of Robert Louis Stevenson's collection A Child's Garden Of Verses.

Alongside the nod to RLS and the Commonwealth Games that took place 4,500 miles away, our repertoire includes folk songs from the British Isles plus music by Lloyd Webber and Benjamin Britten.

In July, I followed a well-trodden path from Scotland to Mumbai, one plied in the 18th and 19th centuries by Glaswegian merchants, ministers and medics working for the East India Company. This year, it has been musicians making the journey between Scotland and India.

In April, the BBC Scottish Symphony Orchestra and students from the Royal Conservatoire of Scotland, led by composer James MacMillan and violinist Nicola Benedetti, concluded their Indian tour with concerts and workshops at the NCPA; in July, a number of Indians headed to Glasgow to perform in the Commonwealth Games cultural festival.

I travelled to Mumbai under the auspices of the Mehli Mehta Music Foundation (MMMF), set up in 1995 under the patronage of the world-renowned conductor Zubin Mehta to honour the musical legacy of his father.

The Mehtas, father and son, were both born in Bombay (as the city was known for most of its colonial history) into the Parsi community. The Parsis, followers of Zoroastrianism, have always been known for philanthropic giving, and in this spirit the MMMF exists to provide tuition and performance opportunities for young musicians.

My task has been to combine the Foundation's own 'Singing Tree' choirs with children from the NGO-run municipal (state) schools and the Udayachal Schools that the Godrej industrial empire runs.

The family-run Godrej firm is one of India's largest and their Mumbai factories make bank vaults, hospital beds, soaps and parts for India's space rockets.

The two schools on the 'Godrej Colony' campus cater for all its 9,000 employees' children, so the choirs include the offspring of doormen, labourers, scientists and hi-tech designers. Another prominent Parsi family, the Godrejs, have always valued the place of the arts and music in their students' lives.

Shortly after my first rehearsal with the municipal school pupils, I visited Dharavi suburb, across a muddy mangrove swamp from the world's largest diamond bourse and Mumbai International Airport.

Dharavi was built as an overflow residential area by the British in the 1880s and is now the second largest slum in Asia, providing work and a home to more than a million people in an area of a little more than a square kilometre. I had mixed feelings before taking an official 'tour': how could my visit not just be seen as three hours' voyeurism?

While I had no anxieties about my safety, I felt distinctly awkward as our group of white, affluent visitors assembled. We witnessed a hive of industry and squeezed through a maze of alleyways that double as open sewers, too narrow for two people to pass by. Despite the very apparent hardships, I have not witnessed more smiles and high-fives anywhere else in Mumbai, and the visit gave an insight into the lives that many of my less privileged choristers lead day by day.

I quickly discovered that monsoon season is not the ideal time to be in Mumbai: deluges are disconcertingly abrupt, barely giving time to run for the cover of a tree. As another downpour approaches Marine Drive, I watch the young Mumbaikers running out into the torrents to welcome the water.

The roads soon become rivers and well-dressed businessmen and lawyers rush between their offices and courthouses in flip-flops. But at least the rain is warm, just like the welcome I have received from all whom I've met in a magical, musical Indian Summer.

Michael Bawtree directs the Edinburgh Royal Choral Union, the Glasgow Chamber Choir and teaches at the Royal Conservatoire of Scotland. Follow him on Twitter @michaeljbawtree