Add timepiece to track song progress.

[Canaanabolaanan]

Playing a song in the middle of the tab should begin at 2:18, for example, rather than 0:00, to better correspond to the actual song's length.

[Ebdim9th]

(As I mentioned on Discord,) also have the counter show 00:00 of say, 04:10, at the beginning when you first open the file.

[cameronwhite]

I think this was difficult to implement at the time, since the midi player was generating midi events and handling repeats / directions on the fly. That's since been reworked and all the midi events are generated up front (basically, creating a midi file in memory and then playing it back), so it should now be fairly easy to know the total duration and current time within the playback.

[Ebdim9th]

Excellent, it'll be a cool addition to work with... I'm mostly just using PT now, it does just about everything I could think of that I want it to....