Unwinding sub-arrays

[tommcgee57]

For example, sub_tracks. In release #10798921 I find this:

...
tracklist:
[ { duration: '7:48',
position: '1',
type_: 'track',
title: 'Overture: Coriolan, Opus 62' },
{ duration: '46:51',
position: '',
type_: 'index',
sub_tracks: [Array],
title: 'Symphony No.3 in Eb Major Opus 22 'Eroica'' } ],
...

The sub_tracks and especially their timings are exactly what I'm trying to get at in my project. How can I accomplish this?