In the church band I recently joined they have up to 5 singers, depending on the day. The rest of the band includes keyboard, acoustic guitar, a couple teenagers on electric guitar, a bass, and a drummer. And of course me as the only wind instrument player. The singers are frequently out of tune. Not sure if they can't hear themselves on the monitors or what, but I have trouble trying to stay in tune with them since I hear 2 or 3 pitches from them. What method should I take to make the best out of this? Also, it is worth buying an electronic tuner at all?