Born in London he studied with his father Aubrey Brain at the Royal Academy of Music and played with the Royal Philharmonic and Pilharmonia Orchestra as first horn.  Composers who wrote works especially for him included Britten, Hindemith and Malcolm Arnold
"Classical Gems from YOUTUBE"
links to valuable videos of him playing on the YOUTUBE Site

BRAIN Quintet for horn, violin, 2 violas & cello in E flat major, K. 407 (K. 386c) WA Mozart Sonata for horn & piano in F major, Op. 17 Ludwig van Beethoven Dennis Brain, Denis Matthews Horn Concerto No. 2 in E flat major, K. 417 WA Mozart London Philharmonia Orchestra Dennis Brain Walter Susskind Horn Concerto No. 3 in E flat major, K. 447 WA Mozart Halle Orchestra Horn Concerto No. 1 in E flat major, Op. 11 (TrV 117) Richard Strauss London Philharmonia Orchestra Dennis Brain Alceo Galliera
DENNIS BRAIN - His Early Recordings Irme Hartman Ludwig van Beethoven Wolfgang Amadeus Mozart Walter Susskind Lener String Quartet Augrey Brain Dennis Brain Philharmonia Orchestra of London Dennis Matthews Sandor Roth Jeno Lener
DENNIS BRAIN  - The Horn of the Century Ludwig van Beethoven Wolfgang Amadeus Mozart Walter Susskind Aubrey Brain Dennis Brain Denis Matthews Philharmonia Orchestra Philharmonia Orchestra of London