No reason why the following should not work for you...this is what I do and it works for me...
1) Plug your phone into your PC via the USB cable
2) Wait for the phone and PC to interact together...should take less than a minute...you will know when the SD Card icon vanishes from the Notification Bar.
3) Pull down the Notification Bar Pulldown Screen...tap the USB Connection, then choose USB Mass Storage Mode
4) A folder should open on the PC showing the contents and folders of your phones SD card
5) Inside the SD card, create a folder labeled "Music"..make sure this is not inside any other folder on the SD card
6) Open the folder on your PC where your music you want to copy to the phone is located
7) Select the music you want to copy, then right click-select "Copy", then navigate to the Music folder on your SD card, open it, then right click and select "Paste".
8) Either unplug your phone from the USB cable, or pull down the Notification Pulldown and tap USB and then select either PC Mode or Charge Only...
the SD card will not be readable by the phone in USB Mass Storage Mode
You should now be able to listen to all of the music you copied over...