Actors need voice training! Period! The End! But of course I'll continue...
Singing lessons, done consistently, are the safest, fastest way to make your voice strong and flexible. Training with a teacher who can give you focused, individual attention and exercises to be done every day, on a regular basis, will move your career forward.
I have a post on my website about two films that show the importance of singing exercises to strengthen the voice. The King's Speech, with Colin Firth and Geoffrey Rush, and Flawless, with Robert De Niro and Philip Seymour Hoffman. I also wrote on my website about your voice fitting your casting. Leading men speaking like men, not boys, and women speaking like women, not little girls. The voice needs to fit the visual.
Actors complain about the Brits coming to America, taking American roles from American actors. Here's one of the reasons why: They receive required, daily voice training when they are enrolled at RADA or LAMDA. When they graduate, they spend approximately two years doing shows on the West End. They have to be heard and understood clearly in the Theaters they work in. They are putting in their Malcolm Gladwell 10,000 hours, honing their craft and working their voices. So, when they come here, all of their tools are sharp.
I hear the argument sometimes that "I'm a film actor, I don't need a lot of volume." Allow me to be blunt: That's a crock of shit! You will be asked for volume, and if you can't deliver, you're toast. The sound man needs to hear you clearly and distinctly, and if he doesn't, they have to do another take. It's so much easier to ask an actor to pull the volume back, than it is to ask them to bring it up. But ultimately, you want to be the actor that knows what the proper volume is, and they have no problem understanding you.
I've been watching a Netflix series that I love, but a couple of the actors talk very quietly and I cannot understand them at times. There have been a few times when what they were saying seemed to be very important, but they mumble. I rewind and turn the volume up as far as I can without disturbing the neighbors, and I still don't understand them, and I have a really good ears! How frustrating is it when your performance is interrupted because of something technical like that? I'm actually surprised that these things made it through editing. Did they attempt ADR?
Think of the scenario where you book a job, it's vocally demanding, and you start losing your voice after the second or third take? No amount of editing can help that. Then you might cost the producers the added expense of ADR, and honestly, it won't sound as good as if it were happening in the actual take. Actors in LA, unfortunately, have too much downtime between gigs, and it's important to keep the instrument prepared so your ready when the call comes for that audition or job that's happening tomorrow, sometimes today.
I recently shot a short film where I was required to yell over 10 screaming actors to "Shut the F*** UP!" two or three times, then deliver a short, very emotional monologue. The director wanted various angles and uninterrupted takes. We did about ten takes. That's a lot to ask of the vocal cords at 2am. Because my voice is trained, I had no problem, and I was singing and teaching the next morning.
A well trained, Broadway singer friend told me his story about booking a cough remedy commercial, and he had to cough through many, many takes. He said that if he hadn't had excellent voice training he wouldn't have made it past the second take.
A student of mine produces and hosts a huge, four day long event in Miami. It involves a lot of announcing and talking non-stop. He's been doing it for several years, and he told me he loses his voice on the first day, every year. He's been working with me for about six months and he just returned from this years event, and he was happy to report that he didn't lose his voice at all!
So, you want to be ready. You want to be at the top of your game. You go to the gym or do yoga three to five times a week to make sure your body is in top physical shape. You're in acting class twice a week to keep your talent sharp. Don't neglect your voice! If you do, it could make all that other hard work pointless.