Movies with sound were introduced in 1931. Songs since then have become an integral part of Indian movies. The western musical instruments were introduced in the movies in the 1940s, e.g. piano, violin, guitar, trumpet, double bass. However, the instrumentlists using these could not read the Indian sargam, and were able to read only the staff notation of music. Music directors thus required the services of those who could write these notations. That brought to Mumbai Frank Fernand, Chic Chocolate, Chris Perry, Sabatian D’Souza, Johny Gomes and Anthony Gonsalves. These people added music notations to the songs. They also arranged the orchestra. Gradually, these people started composing music pieces between two stanzas of the song. Gomes arranged music for Ina Meena Deeka, a 1957 song for C. Ramchandra. Even in Indian songs,  they introduced choir, string and brass section. Sabatian arranged Preetam Ann Milo in 1955 for O.P. Nayyar. He then worked for Shankar Jaikishan ( 1955-75 ). Laxmikant-Pyarelal previously were arrangers, and as music directors, their first movie was Parasmani ( 1963 ). They introduced the concept of big sound.In one song, they used to write the score for 100-120 musicians. Anthony Gonsalves arranged music for Pancham Da. The harmony in the song is decided by a dialogue between the music director and arranger. Some times, even the music director conceives interlude music  but mostly it is composed by the arranger. An arranger experiments a lot. Rahul Burman assisted Sachin Da. An arranger who is conversant with both the Indian and Western music can do wonders.