I politely tell ANYONE that asks for a request (that they provide) that I will not play anything I haven't heard first. The audience is my client, and in my care, and I will not allow the possibility of offending anyone by language or content in a song that's strange to me. I also pride myself on the pacing of an evening ... even when I'm on break - the songs follow a pace that I decide on to keep the flow in the room. It's a science, not emotional. Tell your sonic phoners to come back on Karaoke night.