For a 4 or so month stretch I regularly had 2 keyboardists and loved it!! One had been playing for years and can pick up a melody within minutes while the other was fairly new to music and he stuck to mainly chords. I sometimes had him change sounds depending on the style of song to harpsichord, organ, vibraphone, or violin. The harpsichord was especially nice on the slower 3/4 and 6/8 numbers like Amazing Grace, Only You (Crowder) etc.
In many groups, one keyboardist does rhythmic piano-like sounds, while the other does mainly sustained string/synth pads...
And what you're saying is...neither are playing melody throughout the songs?
Have you listened to her yet? It may surprise you how whatever she does will fit in with what you do. Even when our keyboardist does play the melody it's not overpowering and it's more than 'just' the melody. I start some songs (the aforementioned Amazing Grace being one of them) with an instrumental verse of the keys alone playing the melody. It's absolutely beautiful and really helps make the song special every time we do it. What I'm trying to say here is--try her out and see if you can creatively fit her in. I've had nothing but positive feedback whenever we add a new instrument. God bless you.
Multiples of anything working together is dependent on either specific arrangements or (better) the players working together to leave space for each other and everyone else. Thing is, the keyboard doesn't just have to be piano or organ, so there's a lot of scope for a couple of players to fit together well if they're wiling and able.
Hey--You added a little comic relief to the day
The names also make excellent passwords, Greg, being both memorable and illogical to those without classical reading. And some names sound wonderfully dubious, like Clytemnestra.
Back about 16-17 years ago the congregation we were in had 2 keys players - my wife and another woman (first cousin of CCM artist Ray Boltz) who was not as good at straight piano stuff.
So my wife played a regular piano part while the other played strings or horns or organ parts depending on the tune.
They worked well together.
In our current congregation, my wife fills in only when the other keyboard player is away.
Give them different responsibilities. Neither needs to play melody -- they will only get in the lead vocal's way (unless the lead vocalist is weak in rhythm and needs to hear the melody. Don't laugh -- I've propped up a lot of lead vocalists). The trouble with melody in this syncopated bluesy world is that keyboard is essentially a square thing and the vocal lead is essentially a rounded thing. Vocal phrases grow and taper; keyboards tend to go "clunk."
One difficulty is that there is precious little printed music that shows good fills, riffs and improvisation (sometimes I draw little staffs on the music, or show them visually). A lot of what a keyboard does comes from their memory of music style from past experience. If their experience exists solely of pawing chords at the keyboard, then they need to expand their experience by listening to all sorts of excellent people at the keyboard, by taking classical lessons, or some other means (help! any help here with new Internetty ways of learning keyboard?).
If they are relative beginners, even having one play medium-low keyboard on a piano or guitar sound, and the other one playing a smooth sound like strings or brass, can help avoid a territorial war and at the same time expand the color range of your whole band.