Thanks for your reply Sam. Good to see developers taking part here.
I have been using the "Subtitles" button and was definitely able to add two overlapping titles as you can see in the file "Subtitles.ssa" I saved it to:
[Events]
Format: Marked, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: Marked=0,0:00:05.30,0:00:16.39,Style1,,0000,0000,0000,!Effect,\R\N Grieg - Lyric Pieces\R\N Book 4, Op. 47\R\N\R\N\R\N\R\N
Dialogue: Marked=0,0:00:07.66,0:00:14.52,Style2,,0000,0000,0000,!Effect,Chris Breemer, piano \R\N
Dialogue: Marked=0,0:00:22.52,0:00:29.04,Style3,,0000,0000,0000,!Effect, 1 - Valse-Impromptu
Dialogue: Marked=0,0:03:30.08,0:03:36.93,Style4,,0000,0000,0000,!Effect, 2 - Album Leaf
Dialogue: Marked=0,0:07:16.61,0:07:23.18,Style5,,0000,0000,0000,!Effect, 3 - Melodie
Dialogue: Marked=0,0:10:37.78,0:10:44.67,Style6,,0000,0000,0000,!Effect, 4 - Halling
Dialogue: Marked=0,0:12:16.37,0:12:22.74,Style7,,0000,0000,0000,!Effect, 5 - Melancholie
Dialogue: Marked=0,0:13:01.15,0:13:09.33,Style8,,0000,0000,0000,!Effect, 6 - Norwegian Dance
Dialogue: Marked=0,0:17:25.95,0:17:33.45,Style9,,0000,0000,0000,!Effect, 7 - Elegie
I'm probably still missing something here. But I'll hunt around for the Text Clip function, sounds like it might be less cumbersome and more flexible,