Plenty of good recommendations here, I agree with both the field recorder method (I use a Tascam DR-100 mkiii) and USB interface like a Focusrite Scarlett or MOTU M2. As for storage, I've gone all out...after you lose data once you learn your lesson. For years I used a Mac Mini with an external HD for backup, both drives gave out around the same time. It may be over the top, but I have 2 NAS units, both using RAID. Yes I know RAID isn't backup, but essentially one of my NAS units backs up the other one. I also have all music on various USB drives. I recently got an M-DISC burner so I'll have those both on and off-site. It's certainly overkill for anything that's readily commercially available but I've got a ton of live recordings, some I've made myself, that if I lose them they're likely gone forever. But if you just want to digitize your tape of "Back in Black" none of this is necessary.
