Although it was popular with audiences, Grieg was dissatisfied
with "In the Hall of the Mountain
King" from the "Peer Gynt" music
and wrote,
A. "I got the idea for this piece from a mighty
thunderstorm."
B. "It is melodious and light, like little fairies tripping
around in an enchanted wood."
C. "It absolutely reeks of...exaggerated Norwegian
nationalism, and trollish self-satisfaction."

C. "It absolutely reeks of...exaggerated Norwegian  nationalism, and trollish self-satisfaction."

Explanation:

When the famous Henrik Ibsen’s play Peer Gynt was first performed, Edvard Grieg, Norweigan compositor, wrote the original music for it. The songs featured are among the most recognized classical pieces today, and that includes the iconic "In the Hall of the Mountain King".

The song is supposed to be ironic and satirical, and Grieg hoped that will be known. He did not like the piece at all, and he wrote to his friend about that, stating the song “reeks of cow-pies, exaggerated Norwegian nationalism, and trollish self-satisfaction”. Grieg expressed how unhappy he is with what he wrote and that he “literally can't bear listening to” it, but thinks that irony will be obvious.