A Sinhala film in 1967 was expected to carry six or eight songs. Sath Samudura (සත් සමුදුර, "seven seas") carried two. Both were sung by the same man, W. D. Amaradeva, and neither of them was cheerful. English Wikipedia's summary of the score is unusually blunt for a film article: "Unlike popular films of the time, only a few songs were included and these were of sombre and austere quality."
That restraint was a decision, and the person who made it was the film's music director, Somadasa Elvitigala. When the Sarasaviya awards for 1967 were handed out the following year, Sath Samudura took Best Film, Best Director, Best Editing, Best Male and Female Roles, Best Lyricist and Best Male Singer — and Best Music Director went to Elvitigala.
Two songs and a fishing village
Siri Gunasinghe's film is about fishing families on the southern coast, shot in black and white by D. B. Nihalsinghe. The two songs are සිනිඳු සුදු මුදු තලාවේ Sinindu Sudu Mudu Thalawe — "on the smooth, white, soft plain" — with words by Mahagama Sekera, and පිපුණු කුසුම පරවූවා Pipunu Kusuma Paravuwa, "the flower that bloomed has withered", with words by Gunasinghe himself. The two awards for lyric and for male voice both went to the first of them. Sekera and Amaradeva are the names everyone remembers from that night; the tune under both of them was Elvitigala's.
In 1997 a government committee named Sath Samudura one of the ten best films of the first fifty years of Sri Lankan cinema. Accounts differ on the exact release date — films.lk gives 22 February 1967, English Wikipedia 2 February.
Eleven films
The full list, as recorded by films.lk, runs to eleven titles across eleven years, and it is a remarkable roll of directors:
Sudo Sudu (1965, Robin Tampoe) — his first, adapted from the verse-story by the poet Sagara Palansuriya; Sath Samudura (1967, Siri Gunasinghe); Binaramalee and Paara Walalu (both 1969); Bakmaha Deege (1969, Dayananda Gunawardena); Wes Gaththo (1970, Wasantha Obeysekara); Welikathara (1971, D. B. Nihalsinghe); Sihina Lowak (1972, Cyril Wickramage); Sihasuna and Sagarika (both 1974, Titus Totawatte); and Asha (1976).
Binaramalee was the 200th Sinhala feature ever made and the first drawn from a radio serial — Mudalinayaka Somaratne's Muwan Palessa. It won Best Film at the 1970 Sarasaviya awards, and again the lyric and male-voice prizes went to Sekera and Amaradeva, for රටකින් රටකට පාර අසාගෙන Ratakin Ratakata Para Asagena, the travelling cloth-seller's song that opens the picture. The film's title song, මල් මල් වන මල් මැද පිපි Mal Mal Wana Mal Meda Pipi, was sung by Sujatha Attanayake.
A film that was almost all songs
Then, in the same year, the opposite. Dayananda Gunawardena's Bakmaha Deege — built from his stage play Bak Maha Akunu, itself after Beaumarchais's The Marriage of Figaro — has nine songs, and Gunawardena wrote every one of the lyrics. Elvitigala set them for a small crowd of voices: Amaradeva on ආදර හැඟුම් Aadara Hangum and on the syllable-game සරිගමපා Sarigamapa; Nanda Malini on මලකින් මලකට Malakin Malakata and දියට නැමුණු මල් Diyata Namunu Mal; Amitha Wedisinghe on කන්ද උඩින් සඳ Kanda Udin Sanda; Victor Rathnayake on අවි ගත් මදනායක Awi Gath Madanayaka and බක්මහටයි හෙන විදුලි Bakmahatai Hena Viduli.
Set beside the two austere songs of Sath Samudura, the pair make the point about him better than any biography could: he was not a man with one manner, but a man who worked out what each director's film needed and then supplied exactly that and no more.
Welikathara, and after
Welikathara in 1971 was D. B. Nihalsinghe's first feature and South Asia's first film in CinemaScope, shot at Point Pedro. Wikipedia's article on it says, in passing, that "Somadasa Elvitigala added one more feather to his cap with this film after the beautiful musical score he created for Sath Samudura." Its one song is another Sekera–Amaradeva collaboration, ගිනි ගත් මරු කතරේ Gini Gath Maru Kathare, "in the burning desert of death". The film was later named tenth-best of Sri Lankan cinema's first half-century.
Outside the films, a handful of his tunes survive as songs in their own right — අඩවන් දෑසින් Adawan Dasin, a Sekera lyric sung by Victor Rathnayake, comes from Wes Gaththo; මේ තියෙන්නෙ කන්තෝරුව Me Thiyenne Kanthoruwa, a Henry Jayasena lyric, comes from the stage. After Asha in 1976 the film credits stop.
What is not known
Almost everything else. There is no Wikipedia article about him in English or Sinhala. No birth year, no death year, no birthplace, no account of where he learned music, no interview, no obituary has surfaced in any reachable source — only a filmography, an award, and the songs themselves. The site's own artist database spells his name Somadasa Alvitigala; films.lk, which carries his name in Sinhala as සෝමදාස ඇල්විටිගල, is the record this article rests on.
That is worth stating rather than papering over. A composer can be central to the most celebrated decade of a national cinema and still leave no biography behind — which is one of the ordinary ways a musical history goes missing.