Single-Malt can only be used to refer to those spirits made from Barley Malt. The term "Single-Malt" only applies to whiskies made using that grain. Blended Scotch is produced by mixing several different Single-Malt scotches together (the base of the Johnnie Walker blended scotch is the magnificent single-malt, Cardhu) In a true "Single Malt Scotch" the barley all comes from the same region of Scotland, where growing conditions are carefully controlled. The different environmental factors of the different regions change the qualities of the scotch. This is a similar practice to those in the wine regions of France and Italy.