#2
They're dead notes, lift your fingers off the strings so they're muted and keep strumming. You'll have to be careful with those ones though, if you don't mute the strings with more than one finger you'll get harmonics instead of dead notes.
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#4
Quote by Zaphod_Beeblebr
They're dead notes, lift your fingers off the strings so they're muted and keep strumming.


Just in case some newbies misunderstand this, you don't lift your fingers off the strings, you let up off the pressure so that the strings aren't fretted anymore, yet your fingers are still on the strings for muting. It should produce a quick rhythmic/percussive sound.