Open chord changes are very similar to racing: the chord change occurs as the fretting hand lifts and the fingers move from a previous position to a new position, and sometimes the strumming hand doesn’t even continue strumming while all the hand is moved around. However, the challenge doesn’t stop with just the chords. The beat disappears too, so the music feels broken even if the next chord eventually lands in the right place.
So, select two open chords first and keep the selections simple. No, not a song! There is no verse or chorus or a long chord progression; only two open chords need to be moved to between each other. Then look at both chord forms and see what needs to be moved to change between them. Some chords have an individual finger that remains on the string or very close to the string. In others, all fingers need to move to a new position. When you are able to see the change before playing it, the change will not be random.
Now form one of the open chord shapes and strum the strings gently. Check if you play a clean chord; you do not have to play like a complete professional guitar solo player. If you hear a buzzing on a single string while you strum, try changing the position of the finger just before moving to the new chord, or place the finger in a better position. Then lift your fingers and move them to the next chord. Most guitar players make mistakes here, where the fingers move high up, and the fingers then fall down on the strings just as if you were beginning a new change. By lifting the fingers only as far as necessary for a new chord, the hand stays close to the next position.
If you are able to strum the first and second chord individually and they both sound clean, do not strum for a moment. Instead, form the first chord with your fingers, then lift them off the fretboard. Repeat this until you are able to change the position to the other chord, and repeat that as well. Try not to make any noise during the switch as you are moving your fingers around. In the beginning, it’s a matter of learning your fretting hand what position the fingers are supposed to change between. The fretting hand is not in charge to check how fast the whole change works out. Also, be aware that your thumb behind the guitar neck should not clamp harder during the switch. Extra pressure usually makes the fingers slower.
After you are able to move from one position to another, put the rhythm back into your guitar again, but keep it very simple. Strum only with a single downstroke and count out loud. Continue counting and do not change the pace even if your fretting hand changes late. It may seem a little strange, but the idea is to not lose track of the beat just when your fretting hand has to move. If the new chord is placed a little later than you intended, you do not have to worry too much. You can then adjust the change by slowing the pace. A metronome can help, but only if the speed is comfortable enough that you can still think.
You can also move your strumming hand a little, as a preparation of the next chord. Your strumming hand doesn’t necessarily have to continue to strum during the space of a new chord; it just shouldn’t freeze. A soft movement keeps the beat in your mind. Once your hand moves softly, this helps to strum a rhythmic pattern later because it is clear where the beat is in relation to your strumming hand.
Finally, notice how you strum, because different types of mistakes need different changes. A buzzing on a string can indicate your fingers have not landed correctly near the fret. A rushed rhythm can be because the tempo has been too fast. And if your hand is tired too quickly, you could squeeze more pressure into the neck while your fingers search for a new chord. If you are able to make different changes when you notice your mistakes, you do not have to guess what the cause of the mistake is.
Finally, practice changing between two open chords in a loop, at a speed you’re able to stay calm. The aim is a better path for moving between the two chord forms: fewer finger changes to get off the strings, shorter periods of silence in the strumming hand, and a steadier sense of beat. Once the new chord change feels better, you can change it again by adding a second downstroke or even an upstroke on a later downstroke or the space between a new chord change. The new chord should grow from a controlled change, rather than by trying to rush to a new chord.