So, back on the .m4a vs .mp3 question. I've got a friend's geeky son lined up to convert some cassette tapes I have to audio files. I was asking him about using .m4a because I didn't like mp3 - or so I thought. But if I just ask him to use 224kBit data rate, then I should be OK? (I'm having trouble filling my 8GB iPod, it took the entire Ring cycle as a snack as .m4as.)
He could digitize the audio in uncompressed, CD-compatible format: 44.1 kHz sampling rate, 16-bit stereo, WAV (or AIFF, if on Mac).
I assume the classical music won't have to be cut into convenient 4-minute tracks? Then in the end, you'll have a single, 30 or 40 minute recording of about 300-400 MBytes of data - not a problem for any current USB flash stick.
Working from this source, a) listen to the uncompressed recording to make sure he hasn't accidentally mis-leveled the signal. Distortions in louder parts are a dead giveaway. You'll most likely also not want any of the auto-gain that some converters offer (making quiet parts louder, and dampening loud parts)?
If you're happy with that raw source file, have him convert it to MP3 or MP4. Or you could also do it yourself easily - drop the .wav file into iTunes, check the preferences for the compression settings, then right-click the .wav and pick "convert to MP3".
If you don't like the sound, throw the new MP3 from iTunes, adjust the compression (higher bit rate, or maybe AAC), then compress again. Repeat until happy.
Then keep the MP3 and discard the WAV...