Final answer:
Du Fay wrote several motets for Pope Eugenius IV, including 'Nuper rosarum flores' and 'Se la face ay pale'.
Step-by-step explanation:
Gilles Binchois wrote a large number of motets for Pope Eugenius IV, but the exact number is not known.
One of Du Fay's most simply structured motets is Nuper rosarum flores, which was composed for the dedication of the Florence Cathedral in 1436. It features clear melodic lines and a straightforward rhythmic structure.
The term 'sweet sounding' is subjective, as different motets may appeal to different listeners. However, Se la face ay pale is often regarded as one of Du Fay's most beautiful and sublime motets.