For recording see if you can find a tape player that has a headphone out, like a walkman or a system, then plug a male to male 1/8 from the device into the mic input on your mac. Then if you don't know the recording process, go to preferences, audio midi, make sure audio input is built in line input, and the output is normal. then just press record on garage band and play it on the device. as for it being muffled, try blowing gently on the tape to see if it has accumulated anything weird over the years, but if you can't, garage band has a couple of effects that might help. So you have your real instrument track, open the info panel on the left, click on "podcasting" there's a bunch of presets that might clear the voice up a little. if that doesn't work or isn't enough, click the triangle next to details, then click the little pen icon for the equalizer, then you can cut the low a little, cut the mid and put the mid frequency fairly low, and you can also boost the high, and that will make it a little clearer.
Hope that helps
Jamie
