Soundslice lets you tabs with video so you can see them in real time.
Search for any YouTube video, and you’ll get an interface that lets you slow it down and make fine-grained loops. No need to log in for this basic usage.
Then, if you log in with an account, you can annotate the video with tabs, chord charts, locations of your favorite licks or any other stuff you want. It’s a matter of creating “tracks” and “annotations.”
Soundslice is made by two people, Adrian Holovaty and PJ Macklin. Adrian does programming and PJ does design. Both are guitar players in Chicago.