He had a classical music background, being part of the Bhendibazaar Gharana and receiving training under Ustad Aman Ali Khan.

While the majority of his songs were in Bengali and Hindi, he showcased his singing prowess in 14 other Indian languages, including Bhojpuri, Punjabi, Assamese, Gujarati, Kannada, Malayalam, and Chhattisgarhi.

There he started working as an assistant music director first under Krishna Chandra Dey in a Bengali film Chanakya in 1939 and then under Sachin Dev Burman.

Shankar Rao Vyas taught Manna Dey the songs and he chose to sing them in his uncle's distinct style.

[20] His songs like "O Prem Diwani Sambhal Ke Chalna" from 1944 film Kadambari composed by Anil Biswas, "Dil Churaney Ki Liye from Dur Chaley" (1946) composed by Jafar Khurshid, his duets with Amira Bahee like "E Diniya Jara Suney" from Kamala (1946) and duet song "Aaj Bor Aayee" with Meena Kapoor from 1947 film Chaltey Chaltey became chartbusters in respective years.

Between 1945 and 1947, many Dey-Rajkumari duets like "Hay Gagan Me Badal Tharey" in 1945 for the film Vikaramaditya, "Aowji Morey" from Insaaf (1946), all four duets from the film Geet Govind composed by Pandit Indra – "Kit Ho Nando Kumar", "Chorr Sakhi Aaj Laj", "Apney Hi Rang", "Lalit Labang Lata" from Geet Govind became popular.

He sang for first time songs composed by Sachin Dev Burman, Upar Gagan Vishal and Duniya Ke Logo in the 1950 movie Mashal, which became popular and from here his association with S.D.Burman began.

In the post independence period, after 1947, Dey was regularly used by music composers Anil Biswas, Shankar Rao Vyas, S.K.Pal, S.D.Burman, Khem Chand Prakash, Mohd.Safi from 1947 to 1957.

Dey-Anil Biswas combination gave hit numbers from films like Gajre (1948), Hum Bhi Insaan Hai (1948), Do Sitaare (1951), Hamdard (1953), Mahatma Kabir (1954), Jasoos (1957) and Pardesi (1957).

He recorded his first duet with Shamshad Begum, who was the Hindi female singer most in demand from 1940 to 1961, "Phoolon Ka Swapna" in the films Girls School (1949) composed by S.K.Pal.

Nayyar, G.Ramanathan, T.G.Lingappa, Nirmal Kumar, Ghulam Mohhammed, Bipin Dutta, Rabin Banerjee, Roshan, Sapan Jagmohan from 1954 to 1968.

Rahul Dev Burman made Dey sing the westernised songs – "Aao Twist Karen" and "Pyar Karta Ja" which became chartbusters in 1965.

But the composers who gave Dey consistent popular song numbers in commercially successful films from 1955 to 1969 were S.D.Burman, C.Ramachandra, Ravi, Avinash Vyas, Vasant Desai, Anil Biswas, Salil Choudhury and Shankar Jaikishan.

The solo songs sung by Dey like "Lapak Jhapak Tu Aa Re" from Boot Polish (1954), "O Gori Tori Tu Pyar Ka Sagar Hai" from Seema (1955), "Yeh Kahani Hai Diye Aur Toofan Ki" from Diya Aur Toofan (1956) composed by Vasant Desai, "Humdum Se Gaye" from Manzil (1960), "Aye Mere Pyare Watan" from Kabuliwala (1961), "Laga Chunari Mein Daag" from Dil Hi Toh Hai (1963), classical songs like "Sur Na Saje" from Basant Bahar (1956), "Kaun Aya Mere Mann" from Dekh Kabira Roya (1957), "Pucho Na Kaise Maine Rain" from Meri Surat Teri Aankhen (1963), "Jhanak Jhanak Tore Baje Payalia" from Mere Huzoor (1965); folk based songs like "Kisi Chilman Se" from Baat Ek Raat Ki (1962), "Ae Meri Zohra Jabeen" from Waqt (1965), "Chalat Musafir Moh Liya" from Teesri Kasam (1967), "Aao Aao Sawariya", and duets with Lata like "Masti Bhara Yeh Sama" from Parvarish (1958), "Nain Mile Chain Kahan" from Basant Bahar(1956), "Kehdoji Kehdo Chupaona Pyar" from Kismat Ka Khel (1956), "Tum Gagan Ke Chandrama" from Sati Savitri (1964), "Dil Ki Girah" from Raat Aur Din (1966), "Chunari Sambhal Gori" from Baharon Ke Sapne (1967), were chartbusters in their respective year of release.

Dey gave playback for Raj Kapoor in Shree 420 (Mud Mud Ke Na Dekh), Chori Chori (Yeh Raat Bheegi, Jahan Main Jati and Aja Sanam), Parvarish (Masti bhara hai sama), Dil Hi To Hai (Laga chunari mein daag), Mera Naam Joker (Ae bhai zara dekh ke chalo) and "Ek Paon Chal Raha Hai" from Kal Aaj Aur Kal (1971).

Rafi, Dey sang 101 Hindi songs along with Rafi which include 58 duets with Rafi such as "Ishq Ishq" (Barsaat Ki Raat) "Tu hai mera prem Devta" (Kalpana), "Mama o mama" (Parvarish), Duniyaan ke liye from Maan Gaye Ustaad (1981), "Main Hoon Tera Prem Aur Tu Ho Meri Pran" from Rahu Ketu (1979), the song "Hindustan Ki Kasam" from Hindustan Ki Kasam (1973), "Hum To Tere Hai Deewane" from Johar Mehmood in Hong Kong, "Badey Miya Diwane" from Shagird, "Ye Do Diwane Dil Ke" from Johar Mehmood in Goa, "Agar Dil Dil Se" from Shola Aur Shabnam (1961).

Popular duets of Asha-Dey include "Ye Hawa Yeh Nadi Ka" from Ghar Sansar (1958), "Tu chupi hai kahan" from Navrang (1959), "Jodi Hamari Jamegi" from Aulad (1968), "Sanjh Dhali Dil Ki Lagi" from Kala Bazar (1960), "Aye Kash Chalte Milte" from Manzil (1960), "Na Tohh karvan Ki Talaash Hai" from Barsaat Ki Raat (1960), "Jane Na Doonga" from Dadimaa (1966), "Re man sur me ga" from Lal Patthar (1971), "Zindegi hai khel" from Seeta Aur Geeta (1972) and "Paisa Daulat" from Dharkan (1972).

The popular duets of Geeta Dutt-Dey include both classical songs as well as those which have style of Twist dance, Rock & Roll, cha-cha-cha like "Aan aan milo" from Devdas, :O Mister Suno Ek Baat" from Agra Road (1957), "Karo Na Phere Gali Ke Mere" from Bengali film Gali Theke Rajpath (1959) composed by Sudhin Dasgupta, "Naya Naya Chand Hai Jee" Khuda Ka Banda (1957) starring actor Chandrashekar and composed by S.N.Tripati.

With Lata Mangeshkar, Day recorded around 103 Hindi duets of which songs like "Tere Bina Aag Yeh Chandni" from Awara, "Yeh raat bhigi bhigi" and "Aaja Sanam Madhur Chandni Mein" from Chori Chori, "Pyar hua iqrar hua" from Shree 420, "Woh Chand Muskaye" from Akhri Dao (1958), "Ritu aye", "Dil Ki Girah Khol Do" from Raat Aur Din (1966), "Aya Abdulla Aya" from Juaari (1968), "Soch Ke Ye Gagan Jhume" from the flop film Jyoti (1969) and "main buddho lambo lambo" of Buddha Mil Gaya (1971) are still extremely popular.

Kishore Kumar and Dey had recorded only 6 songs together until 1968 and all proved to be hits, some of them being "Ye Duniya hai usaki nyari hai" from Sauraksha composed by Bappi Lahiri, "Ye Dosti humnai todenge" from Sholay, "Tubhi Piya Chikara Hoon" and "Tu Jaam Liye Jaa" from Bewakoof (1960), "Babu Samjho Ishaare" from Chalti Ka Naam Gaadi (1958) all three composed by S.D.

From 1969, after release of Aradhana, the highest in demand playback singer was Kishore Kumar, so careers of Mukesh, Rafi and Dey were affected and they got lesser number of songs to sing.

His song "Sawan Ki Rimjhim Main" was aired in non-film program section in Vividh Bharati and became popular on the radio.

For Rajesh Khanna, Dey had sung songs "Zindagi kaisi hai paheli" (Anand, 1971), "Tum bin jeewan kaisa jeewan" and "Bhor Aaye Gaya Andhera" (Bawarchi, 1972), "Nadiya Chale Re" (song sung with Rajesh and Dey), "Hasne ki chah ne kitna mujhe" (Avishkaar, 1973) and "Gori tori paijaniya" (Mehbooba, 1976).

Kishore-Dey together also sang with Asha in many films and famous among them are "Khan Chacha" from Dil Deewana (1974), "Aa Kitni Sundar Jagah" from Chandi Sona, both composed by R.D.

Burman and with Lata in "Goyakechu Nanche" from Manoranjan (1974), "Logo Ke Juban Me Apna" from Nehla Pe Dehla, both composed by Pancham.

Several such songs included the duets "Kaanhaa Bole Naa" and "Balma Moraa Aanchaar" for the film Sangat, composed by Salil Chowdhury in 1975, which became very popular and was picturised on Rakesh Pandey and Kajri.

Dey continued to have hit Hindi songs to his credit from 1971 to 1986, such as "Dulhan Banungi" from Who Jo Hasina (1983), composed by Raamlaxman and sung with Lata, "Aankhon Ka Salaam Lo" with Lata-Rafi in Samraat, "Dilwaale Dilwaale" from Kranti (1981), "Yaari Hai Imaan" from Zanjeer, "Ye Duniya Hey Usi Ko" sung with Kishore-Usha from Suraksha (1979), "Tum Besahara Ho To Kisi" from Anurodh (1977), "Jo Likha Gaya Hai" from Umar Qaid (1975), among others.

He worked with composers like Laxmikant Pyarelal, Kamlyanji Anadji, Pancham, Bappi Lahiri, Raam Laxman, Sonik Omi, S. Rajeswar Rao, Ravi, Rajesh Roshan extensively from late 70s to 1990 in Hindi films.

He sang "Bohey Nirontaro Ananto Anandadhara" from the album Rabindra Sudha in 1961, and then went on to sing 14 songs composed by Rabindranath Tagore until 2002 in Hindi.

Yesudas, P Jayachandran, Suresh Wadkar, Kavita Krishnamoorty, Alka Yagnik, Antara Chowdhury, Preeti Sagar, Dilraj Kaur, Yunus Fazmi, Jaspal Singh, Anwar, Manhar Udhas, Joginder and Mubarak Begum.