We don’t usually do on-screen tablature but this can be done relatively trivially inside Final Cut if you can export the tab as an image in a single strip:
In this case I just did that manually by exporting the GP file as a PNG (single click) and lining up the staves up side by side in FCP. Tab and Sierra Hull video are unrelated, just a mockup.
So if you want to script something, all you need to do is script the slicing of the PNGs by a known set of pixel dimensions, lining them up side by side, and exporting as a really long image. That’s probably a lot easier than writing something to read tablature files. Note that you want to enable Bar → System Layout → Fixed in GP so all the bars are the same size and the inter-staff spacing is the same.
Benefits:
Instant export / no video capture. Playhead design of your choosing — in this case a square at .5% scale with a glow effect applied, all in FCP. Scrolling with two keyframes — one at the beginning, one at the end.