Actor. TV show host. Occasional singer. Phenomenon. Amitabh Bachchan, who has towered over the world of entertainment as much as the cultural scene for nearly five decades, turns 80 today.

The ‘Big B’ isn’t limited to his roles—he’s been voted ‘greatest star of stage or screen’ in a BBC poll, became the first living Asian to have a wax statue at Madame Tussauds, was conferred France’s highest civilian honour, and carried the Olympic torch. Likewise, he underscores the famous ‘baritone’, which has its own separate identity.

In its latest outing, the voice—that has launched a thousand brands, drawn tourists to Gujarat, rendered Holi parties incomplete without ‘Rang Barse’—is a household companion who wishes you ‘happy birthday’ and delivers jokes, poetry, even weather updates, all at the tap of a mic and the wake word ‘Amitji’, which brings alive a smart home assistant.

Alternating between rumbling to nonchalant, a pivotal facet of the screen persona has been the sonorous voice that make the most mundane words rich with possibility. Curiously, Bachchan’s stint in cinema as a faceless narrator took off before his career as an actor. After an unsuccessful attempt to land a job at All India Radio, his voice made its debut when filmmaker Mrinal Sen used it for the sutradhar (narrator) in Bhuvan Shome (1969).

The voice box has spawned a cottage industry of soundalikes, prompting the actor to copyright it after a tobacco manufacturer allegedly copied it to promote their gutkha. However, there are impersonators Bachchan himself encourages. Remember ‘Jumma chumma’ or ‘Sona sona’, songs that people think the actor sang?

Sudesh Bhosle takes it as a compliment. “I recorded them in front of Bachchan saab, it’s he who personally recommends me for some of his songs and supervises the recording,” says Bhosle who draws on the actor’s body language. “I need to place my hands on the waist and droop my shoulders to get his iconic ‘hain’.”

Chetan Sashital who dubs commercials in Bachchan’s voice, says he achieves the soundscape by “breathing deeper from the diaphragm… it’s incorrect to define his voice as just a baritone. It’s how he modulates, breathes, pauses and his sharp diction that allows him to switch from a commanding tone one heard in Deewaar to a raspier Sarkar to a grouchy Mirza.”

Both fill in at Bachchan’s behest “when he’s unavailable or his throat isn’t in good shape or after written or oral permission from him.” “His voice is his intellectual property and we have to guard against any mischief or misuse,” says Sashital.

Bhosle adds, “I check with his office to ensure it’s not a brand that is trying to get me because they can’t afford Bachchan saab.”

The industry exists in regional languages too. Some of Kerala’s best mimics are known for their Bachchan impressions. Be it late Kalabhavan Abi who would dub for Malayalam versions of the actor’s ads or Ashraf Thalassery who was his duplicate in the Malayalam movie ‘Guppy’.

It is perhaps his ability to tease out emotions from every word in a “resonant deep vocal timbre,” says sound designer Bishwadeep Chatterjee. “No matter how much he modulates by raising or dropping the pitch, there is incredible consistency in his vocal persona. Never too thin, nor too soft,” says Chatterjee who has worked on several Big B films. “He is so passionate about his dialogues, voiceovers or singing that he’s built a state-of-the-art recording studio in his house.”

There’s science as well to this unique vocal imprint. In the last two years, studies have indicated that taller men are perceived as more formidable, partly because their voices are lower in pitch. Research at Pennsylvania State University confirmed that tall men had lower frequencies partly because longer vocal tracts and larger vocal folds generate lower, more resonant voices while another study by an anthropologist at Boston University found men with low, resonant voices are more likely to be perceived as “attractive, masculine, respectable, and dominant”.

All hold true for the 6.2ft tall actor whose ‘baritone’ was the overwhelming answer to a survey on whose voice people wanted to hear if they dialled a call centre.