You guitar players out there know how important it is to make sure you have the capo on the right fret when playing with a band. For you non-guitarists out there, allow Wikipedia to explain:
A capo (short for capotasto, Italian for “head of fretboard”) is a device used for shortening the strings, and hence raising the pitch, of a stringed instrument such as a guitar, mandolin or banjo. It was invented by the Flamenco guitarist Jose Patino Gonzalez.
Now that you know what a capo is, you must realize that if put on the wrong fret, results of horrific magnitude are at stake.
If the guitarist begins playing in G with a capo on the 3rd fret, that actually makes what he is playing in the key of Bb. But let’s say he put it in the wrong place – like on the second fret. That would mean he is playing in A while the band is playing in Bb.
Horrible, horrible noise could possibly ensue.
About the worst place this could happen would be a church, and it happens. I caught it once when a disaster almost struck.
One worship leader so graciously posted the audio recording of his learning of this capo lesson. He was singing “Holy is the Lord” by Chris Tomlin. When the band comes in, his voice tries to match what is going on and figure out why tonal worlds are colliding and it could be about the funniest thing you have ever heard.
Audio Proof of Why You Must Always Check the Capo
Let this be your warning: always check the capo.
If this happens to you, just stop. Band, stop. Singers, stop. Just stop and pray or something.