I agree, the music selection is the toughest part. I use audioblocks.com for royalty free music, $99/yr unlimited. I really like their method to quickly listen to music. It's fast and efficient, I've never seen anything more convenient. However, it's still tedious to listen to 25 titles to find something appropriate for the video subject. Try finding appropriate music for a fire that's destroying homes! That's not easy, but I found one. I'm always looking for other music sources. Audioblocks is good, but I've used so many of their titles, that I've used some twice because I like the song so much. All of their titles have no lyrics, only instrumentals. Although all music is royalty free with audioblocks.com, I ALWAYS get infringement notices from YouTube that I have to rebut. That's a hassle, when everyone is claiming copyrights infringement on music I've paid for the rights to. My rebuttals always come back OK, with rights released, but it's such a hassle. So my advice on that is, ALWAYS
put the song title and source of the music in the description of YouTube so anyone challenging the copyrights can clearly see where you obtained the music. But the bigger reason is so YOU can remember the song title and where the song came from a month later when the copyright infringement notices appear.
Once I find the appropriate song, that's long enough (typically 3min), I can punch out a video in about 2hrs, complete with transitions and titling, timed to the music. But finding the right song can take 15 to 30 minutes, sometimes an hour.
The song for this below took me 20min to find in Audioblocks, but I didn't really know what I was looking for at the time. When I found this jazz title it reminded me of the TV series Frazier which used a jazz song, and was about Seattle, so that's why I used it.