If you made your first recordings on a 4-track tape machine before migrating to a computer-based DAW, chances are you have dozens of old cassette tapes lying around.
These tapes won’t last forever … Magnetic tape degrades over time, and if you keep them long enough, those old 4-track masters, and the mixed tapes you created from them, will be unplayable.
If there’s any chance you’ll want to hear the old recordings in 20 years, it makes sense to transfer the recordings now to a digital medium, which should be permanent. Lifehacker has a short feature, How to Digitize Cassette Tapes, that details how to accomplish this with Audacity (though obviously, you can substitute your favorite DAW.):
There’s more to this idea than a trip down memory lane. Now that tape decks have all but disappeared from car stereos and Walkmans are a thing of the past, there’s really no other way to listen to cassettes, forgotten or otherwise. You invested big bucks in these things, so why not get your money’s worth? Here’s how to bring your tapes into the digital age.
The Lifehacker article is specific to 2-track stereo tapes (i.e. your mixdowns,) however it’s certainly possible to transfer a multitrack recording to your computer:
The problem is that the Portastudio has four tracks, and most people only have two inputs into their computers. Four into two doesn’t go, so how can these recordings be transferred? The simple answer is to record two at a time. Transfer two tracks, then wind the tape back and transfer the other two tracks.