Symphonie #1 for Organ and Orchestra: Final (opus 42) by Alexandre Guilmant 

This piece is historic! Widor , and a few others , conceived of the ORGAN Symphony ( just for organ) then Guilmant, here, and Saint- Saens , in his brilliant Organ Symph. #3 , and later on J. Jongen, in his equally brilliant Symphonie Concertante for organ and orchestra truly demonstrated the incredible possibilities for this combination. There are a number of other composers who did the same, but these are the real pioneers!!! Each of them,a brilliant composer in their own right , wrote brilliant music !!!!