The purpose of playing the guitar is playing the right music and the right notes, right? Among other things, this is accomplished by having the instrument perfectly tuned within itself. A “B flat” on one string should sound like the “B flat” on any other string of the guitar. If you hook up your guitar to a chromatic tuner and play a random note, the meter should indicate ZERO. There are plenty of reasons that you can have a hard time tuning your guitar. For instance, you can’t tune a guitar with 200 years old dark and rusty strings.
Even if you had restrung your guitar 3 months ago and had never played it, those strings are still considered 3 months old.
As soon as you put new strings on a guitar they start to decay and oxidize. Even if you had restrung your guitar 3 months ago and had never played it, those strings are still considered 3 months old. Depending on how much you play, your strings will last between 2 weeks and 2 months before they should be changed. When your strings are too old you will have problems such as difficulty tuning, intonation issues, buzzing, and breakage. So, instead of going to a coffee shop and buying a latte go to the music store and buy a fresh set of strings for your guitar.
–Babak