The earlier Proms concert on BBC Four tonight at 7.30 pm is a performance of Hector Berlioz's Symphonie fantastique with added elements of theatre, spectacular lighting and choreography as well as Berlioz’s own words about his music.
5 movements rather than the usual 4 for a symphony. The 4th (March to the Scaffold) is the best known and the 5th (Dream of a Night of the Sabbath) is almost as well known.
Composed in 1830 and so the most imaginative piece of classicial music written up to then. It's episodes from a poet's life who has poisoned himself with opium in the depths of depair from unrequited love.
Berlioz wrote a sort of sequel called Lélio which is rarely played nowadays - the poet awakens from his dreams and eventually is able to recover by becoming a composer and a conductor of his own music. Although the music was popular at the time it became dated, hence has all but vanished.