I was playing my guitar with capo on 3rd fret. all of the sudden i heard a sound probably like a string break. But no. Strings were perfectly fine. But the high E string got completely out of tune like it sounded even lower than B. What just happened?
I did manage to tune it up afterwards, and it holds its tuning in pitch now.
The guitar is 3 years old. And the strings are 5 months old.
Let me know what must have happened to the string and why it made the sound?
My guess is it had nothing to do with the capo. The two most likely possibilities is the winding around the ball end of the string might have partially slipped or the string was improperly wound on the tuning peg. Another possibility is the tuning peg for your E string may be damaged or defective. If the string holds pitch after re-tuning you’re probably ok. If not replace the string first then check the tuning peg to see if it is slipping.
EDIT: here is a video demonstrating a good technique for getting a neat and tight winding on a post:
Another thing that might have happened: if you were tuning with the capo on, the combination of downward pressure plus rusty string may have caused the string to bind up in the nut slot. This would result in varied string tension between bridge and nut, versus between nut and tuning post. The action of playing may have helped unbind the string in the slot, equalizing the tension on either side of nut, in which case there would be a sudden change in pitch, possibly accompanied by a ping/popping sound.