The Quwwalis from the film Barasaat Ki Raat are fundoo. It seems Quawwalis were used in movies for the first time in that film. And became a great success.
I have a cassette which has songs from Barassat Ki Raat and Tajmahal. The lyrics for both movies were written by Sahir Ludhianvi and both movies have Quwwalis. "Na To Karawaan Ki Talash hai..." "Nigaah-e-Naaz ke" "Pehechanata hun khoob tumhari Nazar ko mai" "Yeh haal hai in deewanonka.." etc.

The poetry in these songs is generally high-funda but some Quawwalis have towards the end a couple of lines of Hindi ( while the rest of the song is urdu ). In "Na To Karawaan Ki..." for example there are the lines "Bahut kathin hai dagar panaghat ki, Kya bhar laaoon jamuna se mataki..." and some more and there is mention of Krishna and all and then the song goes back to being Urdu. The effect of the blend and of the contrast is altogether very nice.

If you are a old-hindi-songs buff then you have got to listen to these songs.