This is a false dichotomy. In many churches if there was no organ or piano all the singing would be off key.
It works fine in mine.
Have a tuning fork to begin and a leader up front to aid in the key.
Ultimately, God doesn't care if we are off key anyway (of which I often am). But, it isn't like a piano would help me much either.
Where I worship there are no instruments at all. The singing is beautiful. If the congregation tries a new or somewhat unfamilair song it might not sond very good at first but we always have the option of stopping and starting over again with some direction from the song leader.
The NT says to "making melody in our hearts to God..."
No mention of instruments in this instruction.
Is it wrong to use instruments? Can't say for certain but I would not be comfortable in a church that did.
A cappella is beautiful
It's Church of Christ stuff. They consider using "tools" to produce music to be a sin. I was worship music leader at a Christian church, which, for sake of argument, can be seen as a split from Curch of Christ.
The entire "no instruments allowed" thing has been discussed incessently among me and some of my aquaintences. I'm gonna go on record that neither side is wrong. That is, if your conscience dictates that one is the correct course, and that is the one you follow, you are doing right and not sinning, as per Romans.
The old testament is clear about the use of instruments, as I have pointed out before in this thread. And there is nowhere the new testament prohibits it. God gave us brains and raw materials. That's how we get the church buildings we worship in and the instruments with which we make a joyful noise.
Now, if I was to paint a naked lady on my bass, that might be a horse of a different color.
Now that I think about it, maybe we should just all go back to durges and be done with it.