Hi Prophex,
You could in theory hook up any old multitrack to a computer, using various types of leads and inputs. Because the older multitrack models (from say the '80s) tend to favour ” jack inputs, you'll need to buy a couple of ” jack to mini-jack plugs. You can buy them from almost any electronics shop. Then connect the multitrack output to your computer’s mic or line socket and record the input (I can tell you how to do this if you’re unsure).
The cheapest kinds of 4 tracks are the ones that take cassettes. However, hardly anybody sells actual 4 track cassettes anymore; I've tried a number of places in the past, and I've never succeeded. Of course, you can use the standard blank cassettes that you can buy from anywhere, but you will only have 2 tracks on which to record, which is fairly inconvenient.
For modern compatibility and ease of overdubbing, you should go for the kind of multitrack that takes mini discs. However, if you have some money going spare, I would recommend that you purchase a laptop with a fairly decent soundcard that supports ” jack plugs. This is the most convenient, if slightly more expensive option.
Edited by Zawinul, : No reason given.