try the query like this
SELECT artist, count(artist) AS artist_count, [date] FROM song GROUP BY artist,[date] WHERE [date] > " & DateAdd("ww", -1, Date) & " ORDER BY count(artist) DESC
When you are getting 'aggregate' errors it is usually because you need to place the problem field in the group by.Most likely you are getting multiple values (duplicate?) that need to be grouped.Let us know if that works.