My Fender MiM Mustang Bass (with the PJ Configuration) has imo a strange habit.
Normally you expect bass string to get more loose when detuning, resulting in a slightly lower, flatter tone.
Mine does the opposite, namely getting a raised, sharper tone (for example, my E string going towards F instead of E sharp).
What could be the reason for this? And how do I fix it? I also sense that the intonation on my bass is odd. While the G and D string have perfect intonation, the A and especially the E string are sharper at the 12th fret.
A similar thing happens to me. I hang my basses from hooks on my wall and after not playing for a bit they tend to drift towards sharp. I attribute it to humidity and temperature changes near the wall causing the neck to move
If your bass gets sharp while you’re not playing it, it’s almost always the nut that’s tight.
If it gets sharper when you turn the tuner in a direction that it should flatter, does it keep getting sharper the more you turn it? what happens the opposite direction?
That doesn’t make sense, did you mean E flat?
Most mustang basses have saddles that can be adjusted independently. Can you adjust the intonation of the strings that need it?
All three of my basses are prone to going slightly sharp especially the E and A strings when the weather has been hot (88F inside during the day recently) and humid (upwards of 80%). Since when I tune up and play after it’s cooled off somewhat and all the basses will stay in tune and the intonation is fine it’s not something I personally stress over. My assumption is that the heat cycles (or cold to a lesser degree) is causing the wood in the instruments to expand and contract at a slightly different rate than the heavier strings. But if someone knows what’s actually going on please correct me!
As far as the intonation I’d adjust your saddles to see if they’re in good shape. How are the springs? Are the screws stripped out? These are all easy asjustments if a bit fiddly.
If it seems like the strings are binding in the nut can always lube it with graphite and see if that helps. I rub a soft pencil lead in mine.
Hope that helps!
EDIT: The whole going sharp thing initially confused me too coming from my guitars always going flat.
What period of time has this been happening over? It’s been happening regularly for the past 6 months? Or it used to get flatter, but started getting sharper within the past couple weeks?
Is the bass new?
Changes in temperature and humidity will affect the wood of the bass, especially the neck. Subtly changing how much relief there is.
If there are changes in humidity, I find my basses will shift between going more flat and more sharp. If you just got a new bass, it will also change as the wood adapts to the different temperature and humidity of a new environment. It’s especially likely to happen in spring and fall when the weather shifts.
This is also a major reason why you will likely need to retune in the middle of an outdoor gig, because the environment is so different from a climate-controlled house.
Just give it time. Do another setup as the season changes.
All my basses go sharp rather than flat when I haven’t played that one for awhile. I was a bit surprised, but over time it was so consistent that I figured that was just the physics of the strings. But based on the reactions here to your post, I guess that’s not the universal experience. I’m now curious to know what’s happening.
Oh, and to fix your “problem”, use a tuner to get your strings back in tune.
If he lives in zuid limburg ALL the G’s would sound sharp to him …. Sorry cant help it …
On topic: my basses do this as well but that is probably because the temperature in my bass room drops overnight , no problem
It basically happens with every regular tuning moment (every few days). The bass is a few months old, but I do have to say that the summer of 2026 came with a lot of heat waves.
I start to believe that it’s partly the hanging on a wall with a hook and partly the weather changes. I will remember your tip when I will start gigging with this bass.
…. Sorry cant help it …