I never sang with him unfortunately, but have many colleagues who did, and have been told that Leonard Bernstein 'got' voices.

Why?

He breathed with you. You'd think every conductor worth his salt would do this as a matter of course, but I am sorry to report that this is not the case. 

What does 'breathing with the singer' mean? It means that the conductor isn't stuck in his head. It means that you, as as singer, can feel what he is going to do even before you see what he or she is going to do. If this sounds strange, well... all I can say is: spend a lot of time in an opera house and you will know what I mean. What are some of the things you learn in the process? 

1. The conductor that doesn't breathe with you doesn't connect with you. He usually thinks this is your fault.

2. The conductor who doesn't breathe with you demands to be figured out. You stand there looking at her movements, trying to figure out what to look at so you can stay with her beat. Where it is? Her wrist? Elbow? Eyebrow? Trouble is: having to figure it out is the problem. If she would simply breath, the issue would likely correct itself.

3. Breathing = Feeling. The conductor who doesn't breathe is sending his brain the wrong message, one which is telegraphed to you.

4. When the conductor doesn't breathe, you don't breathe, even though you know you should. You stand there stiff, waiting to see what is going to happen. Your logical mind doesn't help you since we are born imitators. We copy what we see. This doesn't make for a lot of fun music making.

5. The conductor who doesn't breathe moves ever faster, mistaking more action for greater meaning. He doesn't leave you any room to breathe.

6. The conductor who breathes with you may not have the greatest stick technique, but you make beautiful music together. It's a veritable love fest. He may have wacky musical ideas, but you'll be game because the musical pheromones are swimming between you.

7. The conductor who breathes is often observed singing, even if there isn't a 'voice' there.

8. The conductor who breathes with you doesn't have to talk very much. Instead, he just shows you how he wants the music to go. Phrasing happens as a matter of course.

9. The conductor who breathes with you thinks with you. Your minds are joined as one. The extraordinary happens. You can be a mile away at the back of the stage, and you'll be in sync.

10. You trust the conductor who breathes. You can relax. You feel safe. You can sing.