Combine yeast and warm water in a 2-cup liquid measuring cup; let stand 5 minutes. Combine yeast mixture, 3 cups ap flour, shortening, sugar and salt in a large mixing bowl; beat at medium speed with an electric mixer until well blended. Add rye flour and next 3 ingredients; mix well. Gradually stir in enough remaining ap flour to form a soft ball.
Turn dough out onto a well-floured surface, and knead until smooth and elastic (about 8 to 10 minutes). Place in a well greased bowl, turning to grease top. Cover and let rise in a warm place (85degrees) free from drafts, 1 hour or until doubled in bulk.
Punch dough down, and divide in half, shape each portion into a smooth ball. PLace on a large greased baking sheet, and lightly press to flatten bottom. Slash tops of loaves with razor blade or sharp knife. Cover and let rise in a warm place,free from drafts, 1 hour or until doubled in bulk.
Bake at 400F for 30 minutes or until loaves sound hollow when tapped. Brush bread with melted butter. Remove to wire racks to cool.