I'm using google drive. It's good for storing band rehearsals (can be done straight from the phone used for recording the rehearsal). The system of file organization is absolutely up to you. You can add related material (sheets, lyrics) to the directories containing your files. You can install google drive app to you PC and then it can automatically sync, while you can edit your files in any software of your choice. Also, you can share this google drive with anyone of your choice, who then can open/edit the files from mobile, PC web browser or PC app just like you can.
15GB for free. More than enough, if you don't want to store large videos (that's what youtube is for). If you have android phone, you already have google account which contains free google drive. You can easily create another account, going by the name of your band, or more of them.
In my opinion, the main difference between google drive (or dropbox and alike) and 'music sharing sites' is that with google drive, you can't play the files if you are not invited. The activity on google drive is 'personal', while music sites offers 'public' browsing, youtube style.