Agreed on the ram. What level does he want to get into? There are many options. I'm a fan of presonus gear + garageband/logic although my friend is into Protools (but that costs some serious $$$). Anyhow, the MDD has USB1, and two FW400 ports (looked it up on lowendmac - I'm not that cool), so he could get into an older presonus 2 channel firebox or 8 channel firepod pretty cheap and take advantage of the built in FW400. On my QS powermac, I installed a usb2 card and am running a presonus a Audiobox via usb2 for home music recording & production and it works well. Truth be told however, I owned both units and the firebox was a superiorly constructed unit to the audiobox IMO - more machined metal, less cheap plastic, fine sound, nice midi leads + 4 speaker outs vs 2, and a front facing headphone jack - all around better unit and I see them going online for 50-60 bucks. A cost effective option IMO. That + max RAM and I think he'd be set unless he likes to tinker. There's always cool things to do to a PM as I've found out

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If he's short on recording software, Audacity is a freeware option that runs on PPC and can float him until he gets into more in-depth software. Anyhow, lotsa cost effective options out there though, so shop around, kick some tires and figure out what he really wants.