Amara:
Amara has a +13 to Perform strings - She should be able to make it continue for a while, depending, of course, on the dice roller :)
Some sanity will need to be applied here but as we're not going to be under threat or distraction, Amara should be able to just "Take 10".
She'll succeed every time and be able to do the entire job in one day.
However ...
Normally you can work for 8 hours per day, but 8 hours of continuous lyre playing? Sounds a bit far-fetched even to me.
As usual, the rules and any sense of reality don't align.