I generally haul in $5k of hardware and $5k of software when I play a keyboard gig, even if I have access to a house grand piano. An electric guitarist probably has as much investment in what he is doing. A drum kit is in the neighborhood of $10k, and a good acoustic guitar is at least $5k. A good cello is more. Setting up all of that equipment takes a bit of time. Loading in and setting up a keyboard or guitar rig probably takes twenty minutes, a drum kit even more. We show up early; it comes with the territory.
Backing vocalists, by comparison, have no equivalent investment to make either financially or in set up. Quite honestly, it seems like sometimes their commitment suffers because they have so little skin in the game. The one investment they could make, that I argue they should make, is in selecting and owning their own microphone.
A microphone is very personal thing. Not only is it very close to your lips, allowing it to serve a dual purpose as both a germ repository and a voice-amplifying device, but not all microphones pair equally well with all voices. Each kind of mic has its own frequency response, its own dynamics, its own proximity effect. All of these are things that a vocalist should care about, and should ideally be matched to the voice.
Vocalists commonly refer to their voice as their “instrument”. By analogy, that would make my fingers my instrument. My fingers are what I warm up; they have the muscle memory. However, I would argue that the piano or keyboard is my instrument. Similarly, I argue a microphone is the instrument that a vocalist actually plays, that converts what their body does to electrical sound that goes down to a mixing board. Even if you don’t like my comparison on the basis that my fingers don’t actually create sound but vocal chords do, a carefully matched microphone is the last step a vocalist could and should take to impact their sound.
If you find yourself singing through a standard SM 58, or even a much improved Beta 58, you really owe it to yourself to check out a Beta 87A if you use traditional monitors, or Beta 87C if you use in-ear monitors.