Grenache, Syrah, and Mourvèdre are the three grape varieties used in GSM blends, which are commonly blended together in the Rhone Valley in the South of France. Grenache adds acidity and bright fruit aromas. Syrah imparts aromas of violets and carnations, and gives wine structure. Mourvèdre adds dark fruit flavors such as blackberry, as well as a gamy, earthy quality.