I tape recorded an interview at, it turns out, too high volume. I want to transfer the recording to my Mac (iMac, Core Duo, OSX 4.11). However, in my previous attempts, the sound on the computer (using Peak LE to record to computer) is distorted.

Is there a way to lower the recording's volume as it is transferred to my computer?

Turn down the audio level on the tape recorder and your audio interface.

if the audio on the tape is distorted there's not much you'll be able to do to salvage it.
of course, turn down the output of the tape deck, or adjust the trim on your interface's input, but that won't change the color of the original recording. you're stuck with that.

Peak LE has some EQ's. they might smooth your sound a bit. try cutting 5 db or so above 5000 Hz. good luck.

Sorry about my earlier post. My iPod Touch didn't seem to let me actually type my response after GDub.

I echo what houston Music has said. There isn't really anything you can do to remove distortion on your existing recording. You need to check your levels as you're recording. It might help to think about whether your distortion is analogue or digital clipping.