Ignore any hard and fast “rules” people will tell you about how to practice music.
For example, to practicing sightreading, you’ll often hear “Never stop, no matter what mistakes you make. Always keep the tempo steady.” I realize this is well-intentioned, since if you’re playing with other musicians or in public you can’t stop. So yes, you do need to develop this ability.
But with sightreading, you’ll need to develop other abilities too, like reading complex chords. And the best way to learn to read complex chords, is to find some chordal music and plod through it, slowly and methodically, until your eyes and ears can “take in” vertical structures all at once. And there’s simply no way you’ll be able to do this in tempo at first. For a while, you’ll need to pause and figure out just what the heck all those notes are! I did this with the Bach 4-part Inventions for 45 minutes every day for a year when I was 17 and I eventually became a very good sightreader, in-tempo and in public. The smart thing to do is to find an appropriate way to practice each skill you want to learn.
Sightreading, like all aspects of music, is actually a combination of skills. Sometimes I’ll just read through a bebop solo, or the RH part of a Chopin Etude, and slow down every time I become intrigued with a particular passage. This develops my musical ear so that when I sightread something at tempo, I can hear the passage better. And the sharper my ear is, the more accurately I can read music at first sight.
The goal is to learn music in the best way for you. With this in mind, choose a musical skill you'd like to improve with, and break it down into it's elements. Then find a way to practice each aspect in turn. If you do this diligently and consistently, you'll be able to combine them all and master that musical skill. Good luck, and remember to have some fun along the way!
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