Hi Olivia,
This iBook was intended for use in word, processing, database type functions, preparing documents and still shot presentations, as well as having "in the field" internet capabilities through its internal modem and Airport Card option.
It still fulfills those functions quite well, albeit a little more slowly than later models.
It was never intended for audio or video editing (which is what Garage Band and iMovie do respectively). Moreover, its inability to drive a DVD properly is a serious impediment to these sorts of activities.
For movie making, the OS 9 version of Final Cut Pro or iMovie would probably function, but you wouldn't be able to get stuff on and off the computer easily unless you were hooked in via Firewire to a network that included appropriate other computers.
For these applications to work, you would have to boot up in OS 9 - Classic won't support them.
I don't know what music making software was around for OS 9. Maybe try googling for it.
Cheers!
Karl