The ghazal is poetry first — couplets of love and loss — and the singer's job is to serve the words. In Pakistan it reached a golden age, and these five voices are the best place to begin.
Mehdi Hassan, the Shahenshah-e-Ghazal, is the foundation — start with Mujhe Tum Nazar Se. Farida Khanum gave the form its single most beloved recording, Aaj Jane Ki Zid Na Karo. Ghulam Ali made the ghazal intimate and ornamented; Iqbal Bano made it monumental (Hum Dekhenge); and Nayyara Noor made it tender (Aye Jazba-e-Dil).
From here, the whole tradition opens up. Browse everything in Urdu, or explore the artists who carried it.