The cause of fret buzz and slow finger-position checking. Put a finger on one string, fret near the fret and pluck the note once. If the note sounds good, keep your finger there and feel how little pressure you actually need. If the note buzzes, don’t just press harder immediately. Check the position of your finger. A buzzing note is often because your finger isn’t close enough to the fret, touching the fretwire, or tilted so that it isn’t allowing the string to vibrate properly. Buzz can be helpful information because it can help you identify exactly what’s wrong. The guitar isn’t telling you that you can’t play; it is more likely a minor fault in your finger position, wrist angle or hand tension. You may play a finger well by itself, on an open chord, but then mute the neighboring string when forming the chord as a whole.
This is why checking slow is better than playing the chord as a whole and quickly repeating it in the hope that it will eventually work out. Remove the problem from the full chord. Pick one chord shape, say, one of the open chords you’ve been practicing, and pluck every single string beginning with the lowest note that should ring. Check each note between plucks. When a string buzzes, keep your strumming hand still and only adjust the fret hand fingers associated with that note. Move the fingertip a little closer to the fret and hold it more upright, while at the same time removing any unnecessary hand pressure on the thumb that holds the guitar’s back neck. Beginners often don’t realize that they’re pressing the flat of their fingers.
This can lead to one note being weak and another string getting muffled. Fingers that are curved generally create more room for the strings. If you notice that you’re accidentally muting a neighboring string, your finger tip may have caved to the side. Changing the angle just a little can clear the string without the need for extra pressure. You do not have to assume a big position for the hand. You only need a slight change to help the strings ring freely. Hand tension might also disguise the real issue. When you hear a buzzing note, the urge to play harder will be strong. This tends to freeze the wrist and slow chord changes. Instead, experiment with your pressure and only apply as much as it takes for a note to ring clearly. Pluck the string once with light pressure, then with the pressure you need.
The fretting hand is likely unaware of the amount of pressure needed to play a note. It is good to teach the fretting hand when a string is being pressed against the fret versus just being squeezed against it. A tuner and metronome aren’t necessary for buzzing checks but always tune up before beginning your practice session. When the guitar isn’t tuned in, then you have two problems to work on instead of just one, as your ear won’t be able to tell the difference between pitch and contact when the guitar is out of tune, and pitch and contact when the guitar is in tune.
If you haven’t yet tuned your guitar, begin there. Slow down the tempo. It is more important to play notes and chords cleanly at a slower tempo, even if the chord progression is full of bad buzzing. End your buzzing check by playing the entire chord once with a slow downstroke. Don’t judge your entire session or check by the results of that one strum. Instead, just note the improvement that the buzzing check made: one less buzzing string, a clear open string, a less tense hand. One thing you noticed is enough for another few minutes of practice.