AFAIK it won’t detect notes. So you won’t be able to “play the game”. But you can easily have the song playing - the notes coming at you in 3D on the “note highway” while the music notation and tabs are scrolling along below the highway. That’s how I have used it - bass only connected to my amp, not the computer.
You can get thousands of songs free- the actual .psarc files here: https://customsforge.com/. Both m.psarc Mac and p.psarc PC files work. Tonelib doesn’t care if the song is mac or pc - only the original Rocksmith games cares about that.
Those are CDLC or Custom Downloadable Content - made by fans, so quality can sometimes be lacking - but mostly it’s very playable even if it’s not 100% accurate to the recording. For me that’s good enough because I want to play the song, not completely copy every note in the recording.
Use the Ignition4Search feature - get it in Mac or PC file format (but not Xbox) - and it will open right up in tonelib for you. Then you can print the tabs to paper or use the computer.
When you are searching for songs at customsforge- you can use a lot of different filters - obviously you want songs with a bass track - and you can specify windows/PC format, you can even select tuning if you want to keep everything standard or something.
Song selection is large - over 50,000 files, but a lot of them are multiple versions of the same song, so I’d say it’s safely 5,000 high quality songs. It skews heavy to hard rock- but if a song is/has been fairly popular I haven’t had problems finding them. There are some weird exceptions, but about 9/10 songs I’ve found ok.
Here’s a caveat: If there is an official Ubisoft released song, it can be hard/impossible to find a custom(free) version. The people who make these are true fans and want to support Rocksmith, so they want you to buy the songs that have been officially released - a sentiment I agree with actually.