I stumbled over this, from JRR Tokien, in his forward to 'The Lord of the Rings'.

"But I cordially dislike allegory in all its manifestations, and always have done so since I grew old and wary enough to detect its presence. I much prefer history, true or feigned, with its varied applicability to the thought and applicability to the thought and experience of readers. I think that many confuse 'applicability' with 'allegory'; but the one resides in the freedom of he the reader, and the other in the purposed domination of the author.

I was also wondering if there were examples of songs that were entirely allegorical as well as those containing allegorical references?