Who won best amiga demo when tribes ( pulse & melon dezign) won best pc demo?
CREATE TABLE "the_party_demo_intro_compo_winners_1991_" (
  "year" text,
  "amiga_demo" text,
  "pc_demo" text,
  "c64_demo" text,
  "amiga_intro" text,
  "pc_intro" text
);
SELECT "amiga_demo" FROM "the_party_demo_intro_compo_winners_1991_" WHERE "pc_demo"='Tribes ( Pulse & Melon Dezign)';