Once you’re in the meeting, click the arrow next to the Microphone icon and click “Audio Settings…”
That will open up a Settings window on the Audio tab. At the bottom on the right, click the “Advanced” button.
Then check the box next to “Show in-meeting option to ‘Enable Original Sound’ from microphone.’
Then close the box to go back to the Zoom meeting window. You’ll see a new option in the upper left of your screen, to “Enable Original Sound.”
Whenever you lead a song, click that button first to “Turn on Original Sound.” Then when you’re done leading and back to talking, you can click the button again to “Turn off Original Sound.”
(If you have an external mic that you can connect to your computer, that’s great — use it! But if not this “Original Sound” trick is all you need).