It sounds like a simple question, but it's actually very controversial, especially among voice teachers and researchers.
Here's a video of one of my favorite Broadway singers, Stephanie J Block, belting on varying pitches, degrees of chest register dominance, and vowel shapes. Not all belted notes sound alike!
Musical theatre casting directors often give character descriptions including if the role requires to belt up to a specific note.
Josh (Lead): Male, 35-45
raised in the midwest, trained in medicine, tempered by two tours as an Army doctor, confident in his work, but less so in his love life, he feels a little out of step in New York City, steady, pragmatic, plainspoken, but with a calm, gentle humor, tenor, belt to an A/B-flat.
(Excerpt from the casting call for If/Then on Broadway)
Therefore, singers need to be able be on the same page as the casting directors of what a belt is in order to be cast. I'm here to walk you through my perspective, which is based on a review of research articles as well as my own personal experience in the musical theatre industry.
First, we need a definition. The most complete description of belting I have come across (that makes sense to me) is from expert vocal pedagogue Jeannette LoVetri (2012). She states that a belt must include these four components:
Vocal Fold Function: Chest register dominant (in layman's terms - "heavier")
Pitch Range: Near or above the traditional passaggio/break
Vowel Shape: Speechlike until maybe the highest pitches
Volume: LOUD!
You may be surprised that common descriptors associated with belting such as "nasality" or "brightness" do not always apply!
We hear a lot about women belting, but here's also some male singers - listen to all the differences in the sounds:
Look out for more in this "What is Belting?" series, where we'll go more in-depth with the components I mentioned here of registration, volume, pitch, and vowel shape!
Want some guidance on what a belt is in your own voice? Almost anyone can learn to belt as long as it's worked on gradually over time. Feel free to reach out to me at melissafordvoice@gmail.com.