Selecting most recent date when dates are stored in another table
Please try the following.

If you need most recent date for every song over all meeting instances:

select song_id, max(meeting_date)
from song_instances si
    join meeting_instances mi on mi.meeting_instance_id = si.meeting_instance_id
group by song_id


If you're interested only in particular meeting (meeting_id = 4):

select song_id, max(meeting_date)
from song_instances si
    join meeting_instances mi on mi.meeting_instance_id = si.meeting_instance_id
where meeting_id = 4
group by song_id