UnScramble this Word: o t s e r o f o?

Questions

Grieg's Peer Gynt was originally incidental music to a play of the same name. Who wrote the play?

In the music of J.S. Bach, one can find evidence of...?

In 1705, J.S. Bach was exposed to a composer who influenced him greatly. Who was he?

Leonard Bernstein's last minute conducting debut with the N.Y. Philharmonic in 1943 launched his career. Who was he filling in for ?

The story behind Wagner's Der Ring Des Nibelungen is drawn from...?