Hi Ted
Funny that you heard a song from Four Freshmen. They were some gurus for me on the 60:s, in harmoniesinging. The most spectacular with them is that they don´t keep their given harmonies all the time. They change harmonies between each others during their singing. Very oustanding and very difficult, I promise. I have about 10 old vinyl LP and som EP:s too, with them.

About Blues. The harmonies is very hard to explain in letters. They use a lot of 7th, 9th together with sometimes, disharmonic notes. Our sitefriend here, Bill Norrie, sent me an MP3 file of "At last", for about a year ago. That was a good exampel in how they could made some bluesfeeling with male and female voices of this old Millersong. If Bill read this, he maybe can send a file of the song to you.
I belive that the advice you got here, about some notebooks, it´s a good choice and a way to began.
Lindoz