user: Question: How many original artists were there for the Group Performance?
Columns: ['Week #', 'Theme', 'Song choice', 'Original artist', 'Order #', 'Result']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Audition', "Auditioner's Choice", 'Unaired', 'Unaired', 'N/A', 'Advanced']
SQL:

assistant: SELECT COUNT("Original artist") FROM "Table" WHERE "Theme" = 'Group Performance';