"Somewhere" is a song from the 1957 Broadway musical West Side Story which was made into a film in 1961. The music is composed by Leonard Bernstein with lyrics by Stephen Sondheim. from the ballet Swan Lake. The Shadows did a version in 1966.
Hi Ger, I think your synopsis is a bit misleading. It is generally argued that the tune makes a reference to a passage from Swan Lake,and also references a phrase from Beethoven's Emporer Concerto, again with small differences. Your statement might be read as suggesting the whole tune is taken from Tchaikovsky.