Music

Question

In previous posts the Rav made the following points: "Music is technically prohibited all year due to the destruction of the Beit Hamikdash." "Music is permitted when the circumstance requires it. If someone is sad, or children in a car, and many similar situations it is OK." "Also classical music is not a problem." I understand, I think, using music when someone is sad or fro choldren is not to produce simcha but to remove sadness or to calm children. I would like to understand the way "classical music' is differnt from "other music". 1- How is classical music is different and therefore, "not a problem"? 2 - How is Rav Abadi's Sefer progressing? I am looking forward with great anticipation! Thank you!