I can buy poetic truth because poems are composed of words but what is musical truth? My Aesthetics Tutor at Lancaster University informed me and fellow students that people listening to music sometimes remark, "How true!" - so apparently it is a philosophical question what they might mean by this. My response was, "Do people really say that? Well, if they just didn't say it, then we wouldn't have the question of what they might mean by it!"
I have sometimes wondered what it would be like to see a film of events that I had been involved in. The nearest I came to this was a trailer for a film about Margaret Thatcher that showed political events that I had lived through. Conversations, which we cannot remember in detail anyway, would have to be fictionalized. A television "docudrama" showed a British Prime Minister speaking one sentence that he was documented as having uttered whereas the author of a historical fiction would compose fictitious, although hopefully authentic, dialogue.
Shadowlands, a stage play about CS Lewis became a TV play, then a feature film, then a novelization of the film. In the film, the number of Joy's sons was reduced from two to one. Relatives of Lewis, having seen one of these dramatic presentations, commented that the conversations were made up, the actors did not resemble the real people and the order of events was changed and simplified but, despite all this, it was true. I can buy this although perhaps philosophically the word "authentic" is more appropriate.