I was just having a relisten to The Lapse - great band

http://www.youtube.com/watch?v=FijafHq_jZM

although Chris Leo (van pelt & native nod) is the main singer he gives up singing rights on 3 or 4 tracks on both albums to Toko Yasuda

http://www.youtube.com/watch?v=kEGT3_WtSLk

Toko's other bands Enon & Blonde Redhead both do the same thing, with different singers taking the lead on different songs (so not so much duets or duel singing like "the knife" or occasional guest spots)

can we think of some others?