It was a group known as Les Double Six (The Double Six) of Paris.

If you have Realplayer, you can hear one of their numbers here.
I first heard them when I was about 13. I didn't pay much attention at the time because I didn't recognize the artistry as being such. They are WOW. A year ago their name popped into my head for no reason I can determine and I looked for their CD. Had to get it 'special ordered'. They are phenomenal--if ya like jazz at all. I gave the CD away and this thread has remined me to get another. Thanks, Michelle.