Not many people were impressed by a speech delivered without previous preparation.

One word substitute is Extempore.

Epilogue: a section or speech at the end of a book or play that serves as a comment on or a conclusion to what has happened.
Prologue: a separate introductory section of a literary, dramatic, or musical work.
Soliloquy: an act of speaking one's thoughts aloud when by oneself or regardless of any hearers, especially by a character in a play.
Extempore: spoken or done without preparation.