Copying files within folder without the folder to another folder

How can I copy the contents of many folders into another single folder without copying the folders themselves?
I have 900 mp3 files in 50 folders and I want to copy just the contents of each folder into a master folder without the folder there are stored in so I have a single 'list' of songs.

Opening 50 folders and doing a select all, copy, paste is very tedious and the probability of missing a folder is high.

 

XP Pro w/sp3
Never thought of using search.

The other problem 90 of the 870 files didn't copy. Without going through all the files to find which ones are locked, how do I attack this? If I select all 50 folders and look at Properties, nothing shows.

 

Do the search and copy again- check for locked files with Unlocker.
Alt way - copy the root folder and use suction.
http://drnathan.teamhackaday.com/software/suction/

 

I did a serach, selecetd the folders I wanted, copied them and all the files copied where they did not before doing one folder at a time. I even went back and recopied each folder to see if I missed a folder (I missing only one). I was still 70-80 files short.

Why did all copy using the search list, but opening each folder up individually missed some??