This is a right hand practice technique which works extremely well for nailing down a repeating arpeggio pattern.
Loud and Soft
It feels different when playing loud or quiet. Practicing quietly feels almost like your fingers are floating, and it takes a lot of control to not have certain notes accent; practicing loudly gives the impression of fingers flying wildly and it’s a challenge to avoid crashing. Practicing quietly makes it easy to go quick; practicing loudly* feels heavy, awkward and slow.
In short, it’s a good idea to practice a pattern both as loud as possible and as quiet as possible. It forces your hands to go further than may be necessary on a pattern and makes that pattern more secure at a normal volume.
The concept is easy. Keep playing a right hand pattern, start quietly, slowly swell to as loud as possible, then take it back down. It’s hard to actually do this. The benefits is the same as above: takes the pattern further than necessary and teaches control and makes the pattern more secure.
Not everyone can jump right into this right away, but it can be built up. Start with just two dynamics (piano and forte) and keep alternating between them every few patterns, being careful not to stop. Then add in another dynamic level: start piano, then play mezzo forte and finally forte, then step back down. Then mezzo piano can be added in making four steps. Finally try swelling up and down more naturally.
The whole idea behind using dynamics as a strictly practice method is to develop control. The Crescendo/Diminuendo technique is very close to guitar magic (seriously,it’s that good) because it’s develops some extreme control. Try it out! Let me know how it works!
*Loudly and Forte, in this article, mean as loud as possible. In the same way, quietly or piano mean as soft as possible. Sometimes piano can even mean sort of ghosting (barely playing) the right hand.