Actually that’s quite easy, plug your ipad in and go to “my computer”, and you will see your ipad appear as a device, click in and there’s a folder containing your music and another containing your videos. Those folders might not have a name that easily guide you to them but please patiently look at it, you will find the music you need ,then copy and paste, done!
Sometime the data you plug in will become hidden on your computer, you will need to change some settings to make them unhidden.
And here's an article explain about how to transfer ipad music to computer,http://www.levesoft.com/how-to-transfer-music-songs-from-iPad-to-pc.html
you can take a look.