Here a recording before a wind band sings
Bb Harmony Part 1

Here a recording during a wind band sings
Bb Harmony Part 2

Here a recording after a wind band sings
Bb Harmony Part 3

Isn’t the answer obvious? 🙂

Why do you sing?
Singing helps you to internalize pitch. It gives you more confident when you are playing a piece of music. If you have the mental pitch inside your head, is like you know what going to happen = confident, and vice versa.

The solution to get a sonorous sound is by balance and tuning the chords to the fundamental of the harmonic series. Of course, with a listening ear from the musicians will do a better job.

If you can’t sing = you can’t play = you can’t perform!
If you can’t sing = you can’t buzz = you can’t play = you can’t perform (Brass players)

Of course, there are exception to it. But these are just general guideline for most secondary school band members 🙂