I have an acoustic guitar and I always leave it tuned over night until someone told me that it ruins the strings and the neck of the guitar. Is that true and should I leave it tuned overnight?
I leave all ten of my acoustic guitars tuned all the time. In most cases it is not a problem to leave your guitar under the full tension of standard tuning for days or even weeks at a time.
However, if you know you will be storing a guitar for an extended period of time (months) without playing it or changing the strings, it is probably a good idea to de-tune or reduce the tension on the strings. Even with the truss rod compensating, constant tension over an extended period of time can in fact warp the neck, particularly if atmospheric conditions (temperature and humidity) are not ideal.
I have a Yamaha FG-110 that I left stored in it's case in a closet for years without loosening the strings and the neck warped beyond the truss rod's adjustment range and the guitar became unplayable.
Keep in mind that the truss rod exerts tension on the neck as well so if you remove much tension from the strings you should also loosen the truss rod to remove that tension - thereby leaving the guitar in a neutral state with zero tension. This is for long term storage only. Temperature and humidity levels must also be optimized and monitored for long term storage of guitars.
But tuning and detuning daily could potentially exert excess wear on the tuning gears and all the moving of the neck back and forth could weaken the neck like bending a stick back and forth until it breaks. Tightening and loosening the strings daily might also exert extra stress on the strings and damage them or reduce their life.
So to your friend, it's possible that detuning the guitar and re-tuning every day could do more damage to the guitar and strings than simply leaving them in a constant state of tension.
I don't know any guitarist who make a habit of detuning their everyday guitar's every night. I'm not going to do it. And I don't think you should either.
Imagine what chaos there would be in a guitar shop close to closing time every day! And even worse at opening time! Just smile sweetly at your friend, and let him carry on wrecking his guitar and wasting his time, but realise that actually you know far better and leave your guitar in tune for the next day. I've done it with about 20+ guitars for 50+ years, no problems. It wasn't April 1st that he mentioned it, was it?
Leave it tuned, not only will the strings thank you for allowing them to 'settle in' to their proper tension (think of repeatedly bending a coat-hanger to break it) but the machine head gears will also not suffer as much slippage in the long run. The wood and glue is also better off staying under tension. The only time where all the strings should be removed or totally loosened is during major repairs.
When replacing all the strings, do it one at a time
It is advisable to loosen all the strings by no more than a half a turn or so (enough so that when picked they still barely carry a note but still are tight.) when you will be changing altitude quickly. Think flying; in an airplane and the instrument is not carried in the cabin, this is due to rapid atmospheric pressure changes.
If you have to store your guitar for any length of time (months or more) loosen the strings as above and make sure that it is in a climate controlled environment.
When tuning your guitar use an electronic tuner, a tuning fork, or some other reference tone until you have some practice. It's very easy to gradually allow the guitar itself to rise in pitch, therefore over tightening all the strings and stressing out the entire guitar.
hope this helps!
Your friend has heard something about old-fashioned longbows which must be unstrung after use.
A yew bow will deform if it is left for a long time under full tension. Thus it becomes less useful as a bow.
When it comes to guitars, they are designed to be under tension. In fact (depending on the type of instrument) the neck may form a reverse curve when the strings are removed.
Unless you intend using your guitar to shoot arrows, I recommend keeping the strings under tension.
Yes you can.
Actually periodically (day by day) tune and detune the guitar hundred times a year and thousand times by its lifecycle may harm your neck way with much greater possibility than leaving it alone. Tuning and detuning is always a kind of stress for the neck you do not want to do this unnecessary thousand times.