user: Question: Which song was sung by Artist Luther Vandross in the Week Top 20?
Columns: ['Week', 'Theme', 'Song Sung', 'Artist', 'Status']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Top 24', 'Semifinals Top 12 (Men)', '"You Are My Lady"', 'Freddie Jackson', 'Advanced']
SQL:

assistant: SELECT "Song Sung" FROM "Table" WHERE "Artist" = 'Luther Vandross' AND "Week" = 'Top 20';