CREATE TABLE table_821 ("Year" FLOAT, "Winner" TEXT, "Language" TEXT, "Artist" TEXT, "Song" TEXT, "Points" FLOAT, "Margin" FLOAT, "Second place" TEXT, "Date" TEXT, "Venue" TEXT, "Location" TEXT, "Participants" FLOAT)

who is the artist performing at heineken music hall?
SELECT "Artist" FROM table_821 WHERE "Venue" = 'Heineken Music Hall'
SELECT "Artist" FROM "table_821" WHERE "Venue" = 'Heineken Music Hall'