Elvira Madigan was a Swedish film made in 1967. The song that was featured in the movie was Piano Concerto No. 21.

There is no such concerto. Mozart wrote several piano concertos in C major, among which the famous KV 467 (Piano conc. no 21). KV 333 is a piano sonata in B flat major.

Elvira Madigan was born in 1867.

The music is by Antonio Vivaldi - "Concerto for Violin and Strings in

E Major, RV 271 (L'Amoroso), first movment"

It is on UTUBE

Which composer? Mozart's concerto no. 23 in A has its second theme in E major, and in the recapitulation it returns in A major. Schumann's concerto in A minor has its second theme in C major, returning in A major for the recapitulation.