Bennett's Business

On why he practices scales every day

It's based on the vowel sounds A, E, I, O, and by doing that, you just warm up. ... Because every day you really feel quite different. By doing the scales, you get a center, and all of the sudden you feel in control of your voice, where it's relaxed. And it takes about 10 or 15 minutes.   
I don't sing operatically, and I sing very intimately, but I still do the scales, and I think in terms of intonation and making sure that I'm hitting the notes right on the head ... and having it appear quite effortless. 

From an NPR interview which you can listen to here. Another insightful quote below...

I was very fortunate, after World War II when I returned to the U.S., to be able to have some remarkable teachers under the GI Bill of Rights and was able to study at the American Theatre Wing. It was there that I worked with Pietro D'Andrea, who taught me the Bel Canto technique, which is what opera singers use to preserve their voice and it has absolutely helped me over the years.

And just look at that open face....