Hi there. I actually found this little gem of a trick by accident but try this.
1) open GarageBand, choose create a new song. Use the audio recorder instrument. Make the track as long as you want and then flip from the individual track view to the overall project view. Basically you'll have a picture of a microphone with just a long empty zone.
2) minimize but don't close GarageBand. Just keep it in the bottom. There is an audio recording app called DAW that I'm not too crazy about but has two great benefits. I believe it's still free. There are paid add one but you only need the bare bones app since you really won't use it. Lets pretend you have this app installed already.
3) I use the APP downloads HD quite a bit. Is basically a copy of the iPod but with more options. Not important though.
Any track you may want to import to GarageBand, and I mean literally anything, can be pumped into GB with no tedious sync or frustrating file searching. E mail whatever track or song you want in GB to yourself. Dropbox works great with this too as you can choose to open files located in Dropbox with other apps.
4) when your ong of choice is in your inbox or Dropbox or wherever, just long hold it to get that option asking where you want to open the file. Here's the magic. DAW is one of your choices. Select it.
5) this takes you right to the import section of DAW. It's literally fail safe. Under the imported file it will say import(copy) delete, and something else. I can't remember. Choose import.
6) any file that DAW imports will be converted to m4a and amazingly be copied to the general paste board.
7) now switch back to GarageBand and your empty track. Simply click on the empty track, select "paste", and presto, your song has been imported to GarageBand for you to tear apart or build what you will.
I hope I didn't confuse you. I tend to ramble. Feel free to e mail if you have questions.
Weapynx34@gmail.con