Hi 
Thereās something happening with my classical acoustic guitar. I tune before playing it and then apparently it can detune for no reason, it doesnāt seems to always do it but happened to me today: after playing for a little bit the A chord started to sound weird so I decided to check and it was indeed detuned. Why this happens? Itās a cheap but settled up guitar. I will take it to the luthier for another problem but I can check this problem with him as well but Iām curious, it is something complex? Maybe I can fix it but tightening or loosening stuff 
?
1 Like
Nylon strings are quite stretchy and take a fair while to settle in
1 Like
They are not new, nylon strings takes that long to settle?
1 Like
They can be very stretchy. Hang in there.
1 Like
It happens to my steel string acoustic often. Iām no expert, I think itās due to humidity and temperature in the environment, which causes the timber to move. Itās nothing to worry about, guitars are designed to give with the stresses and strains that arise.
1 Like
Interesting
It takes a little while, at least a few hours Iād think, for temperature and humidity to affect tuning. In an inexpensive guitar, Iād be more inclined to suspect cheap tuning machines that are slipping.
3 Likes
That would make sense. I have a cheap guitar also.
1 Like
Iāve read that a poorly cut nut can also be problematic - the strings stick.
2 Likes
On steel string guitars short term tuning changes are almost certainly due to temperature changes in the room. Steel strings respond almost instantly to temperature changes. Take an in-tune guitar from a cold room into a warm room and the tuning will go flat. And vice versa.
3 Likes
Regarding temperature, even sliding your fingers up and down the strings while playing generates friction and heat on the strings, which can cause a slight detune after the first song or two.
2 Likes
It sounds pretty normal to me. Strings need to be tuned. Justin recommends tuning every time you pick up the guitar to play.
Sure, you may have slipping tuners, but that usually would only noticeably effect a couple of strings. You can also have unstable wraps on the peg.
Temperature and humidity seem to be most common. If they are stable, my strings are closer to being in tune, but here in colorado we can have significant changes and they are effected by how often and for how long we leave doors and windows open. I think (conjecture) nylons strings themselves as well as the guitar can be susceptible to temperature and humidity changes.
Add to the temp and humidity a common āsticky nutā and weird changes happen. Out of tune, tune up, then the string clicks and you are way sharp. Sometimes I think there temperature changes over night move the guitar but instead of getting back to normal in the morning, some string stick and so donāt.
Finally, if your strings are getting old, they stop holding tune as easily.
1 Like
Happens almost every time (specially I think with B and G strings). Putting some graphite on the nut didnāt helped that much.
I think it is caused by the very front edge of the nut slot being high, or a slightly small nut groove for your string gauge.
If you arenāt comfortable messing with the nut, a luthier or guitar tech could probably fix it pretty quickly.
I am not comfortable doing much to the nut, but I have successfully opened up tight groove or rounded the front edge of said groove using a set of small welder tip cleaners.
Recently I noticed I was struggling to fret the second string C (1st fret) cleanly. I finally figured it wasnāt my pinched nerve and numb finger tip, but that the string gauge (B string 17 on this set) was sitting at the top of the groove in the nut, not the bottom. I happen to have a micrometer left to me by my late father in law, so I was able to find which of the welding tip cleaners was just bigger than the string and clean up the groove so the string fit. Delicate, to not change the groove angle, break point and depth, but I managed and it is much better now. If I had messed up, it would have needed a new nut. Not the most expensive repair, but the hassle and time without the guitar annoys me.
I have the same problem it only started during the current hot weather in the UK I tend to play in the bedroom with the window open after a while it goes out of tune, during the night the temp drops and its out of tune next day.
Hah ā me too. All I got out of that experiment was a sparkly 
fret board ā¦
I have two guitarsāan old one with a bone nut and a new one with plastic. The bone one sometimes sticks (and got the sparkle treatment), the new one does not (and maybe it is just the shape of the groove in the old nut).
At any rateāplaying steel strings, I too notice the detuning.
Iāve seen videos of perfomers tuning during the performance of a song
To (mis)quote Monte Python, āCarry on Brother Maynard!ā
Bruce
1 Like
I ran into this along with the G string breaking frequently, I completely went over the guitar, fret board etc. with no luck. So I asked the owner of a local music store about it and he suggested changing over to DāAddario Pro Arte stringsā¦problem solved. And yes nylons seem to stretch forever but it is the nature of the beast. Good luck!
What strings had you been using? I canāt tolerate the DāAddario Pro Arte G string. Thumpiest bugger I have ever heard.
My guitar is warm in nature and I really like Aquila Sugar on them. You need to learn not to squeak them and my high e breaks sometimes, but the sound is exquisite. (And no plastic!)
I also like Curt Mangan NT nylons. They are a little mellow on this guitar, but great strings, never have broken one unless I was turning the wrong peg (
).