Players can write to you through GLAR. You get the message by email with the player's name and chair, and you can just reply to it.
Messages to "the band leader" go to everyone who runs the band.
Players who sign in to their own page can also write a bandmate, if you allow it. Open your band from Bands and tick or untick Let players message each other through GLAR, then press Save. When it's off, players can only write the leaders.
A bandmate gets the message by email with the sender's address as the reply-to. Neither one sees the other's phone, and GLAR never shows email addresses on its pages.
Each player can send a set number of messages a day (10 to start). The site master sets that number for the whole site; 0 turns player messages off.
Messages between players show in your Outbox.