Nice Xerox! What about songs still playing after map change in loading screen? Any possibility?
No because thats done client side. Nothing we could change from the server side.
IIRC, musics were still being played during loadings pre-v3.0.9a (aka the update that shipped v3.1's music engine and allowed Jouxbox to function).
The reason of why "networked streams" can't be played during loadings is simple: when Jouxbox (or anything else) gives the order "play that network stream" to a client, it needs to perform a series of checks and operations as fast as possible. Common checks and operations are stuff like "Can I access that music?" (this means checking if your Internet connection can query the stream on the server and access it for reading purposes), "Can I read that music's format?" (because I know some "lambda users" will try to "play images/texts documents"), "Can I understand/decode that music?" (aka it's codec), "Is my buffer filled enough so I can play the music or do I need to do more buffering?" (same principle as watching a stream or a video on YouTube, if the buffer isn't filled enough, then we must pause and wait that the buffer is filled again to play the rest).
Like I said above, all of these checks and operations must be performed as fast as possible. If it's done too late or too slow or not done at all, then there will be risks that the music engine will be "confused" and by extension cause problems. In the main menu and in-game, it's easy to ask something to be updated every frame (when the client asks the engine to render a frame, we update the music engine there). Loading is another story because your client is entirely focused on loading the assets rather than rendering, processing input... (that's why sometimes during loadings your cursor won't move at all and/or Windows will think that "zps.exe stopped working").
v3.0.9a was supposed to have a "loading music" feature à la Contagion/No More Room in Hell (local files only tho). I had to disable that feature because of major bugs caused by HL2:DM's code being a nuisance. I re-enabled it for v3.1 since it's working as intended.