iOS Transfer can help you to solve this problem immediately. iOS Transfer also can transfer files between computer/iTunes to iPhone, iPad, iPod Touch. It supports both of Windows and Mac version. You can download the trial version below:
Easy Guide: How to Transfer Music from Computer to iPad
Step 1. Install iOS Transfer and connect your iPad to computer
There will be an interface pop up while you connect your iPad, because iOS Transfer can search your device automatically. This interface would be like this picture as follow, the name of your device will be in the top left corner, and the appearance of your iPad will be shown on the right side, some information like the type, color, battery and more you will see.
Step 2. Add more songs from computer to iPad
On the left column, you will see the "Summary", "Playlist", "Music" and more. And conversely, the number of files will behind them. Click "Music" button that the names of songs will appear on the right side immediately. There is a "plus" icon on the topmargin which is the second button, then click "Add" button, the folder browse will pop up, so just choose songs you want to transfer from computer, click "OK" button on the right lower corner when you make sure the transferring files. iOS Transfer will transfer your songs from computer to iPad automatically.
In short, why not to download iOS Transfer (Mac) now, then go to enjoy music with your friends at parties or on vocation. You can download the trial version first to enjoy yourself. iOS Transfer can support both of Windows version and Mac version, and of course usefully to iPhone and iPod Touch.
Note: iOS Transfer just can't transfer photos from computer to iDevices.