A few posts ago I mentioned Linux software synths and the wide range of choices on that platform. The unsaid implication was that choices on OS X PowerPC suck by comparison, but that's not totally true. So I thought I'd point out a few software synths freely available on Tiger to get your inner musician musicianing.
Of course, pro DAWs like Logic come with their own synths, but if you're looking to get your feet wet, these plugins should keep you occupied. And they're all AU plugins, not standalone synths, so they'll work in an AU plugin host like GarageBand.
First is Automat. It's a three oscillator synth with an easy to use interface, a few dozen presets, and a great randomizer button to produce sounds you'd never think of yourself (mostly for good reason). This looks good for a beginner, though that doesn't necessarily mean you'll outgrow it.
Next is TAL-Noisemaker. Its sound is "fat and full" and especially good for baselines and also for arcade sounds. Its GUI is a bit CPU intensive, but it comes with a couple hundred presets and plenty of filters. Download the .component.zip 32bit version.
Finally there's Crystal. I had a hard time finding a version 2.4.9 that would run on Tiger, but I finally did here (there's also a CNET download link that says it's 2.4.9, but it's actually 2.5.1 which requires Leopard). Crystal is more complex than the previous two. It's got a manual I'll need to study, but it's been around forever and many people swear by it (not at it).
And finally I'll leave you with this video telling you everything you need to know to make electronic music:
How To Make Electronic Music Tutorial BY DJ NICO MALO
"Minimal effort and no talent." This man is my god.