Start with the simple checks. Make sure every string sits in its nut slot and saddle, and that ball ends are fully seated at the bridge.
Then consider what changed:
- Lighter gauge: less pull on the neck. A small truss rod adjustment to add relief often fixes it.
- Heavier gauge: more relief and higher action. Usually less buzz, but bends get harder.
- Lower tuning: has the same effect as a lighter gauge.
- Old strings to new: new strings ring brighter and longer, so existing buzz can become audible.
Buzz in one spot that doesn't move points to a high fret. Buzz everywhere usually points to relief or saddle height. Buzz on open strings only can point to a nut slot cut too deep.
Make truss rod adjustments in small steps and give the neck time to settle. If you're unsure, a technician can do a setup. On bass, see our bass-specific buzz article.