The default Songs folder is in the root folder Fret Smasher Alpha\Music
There you can create Sub-folders like "Guitar Hero" or something like that, you can organize yourself
For this career you need to download the DLC Pack too!!! Don't forget about that

I got a Hash error and was wondering where do i place the files from the pack source? I already extracted them into a separate folder but not sure whether to place the folder in next to the Fret Smasher folder or do I put it in a specific folder?