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what scales and chords do you think is a must know to be a good guitarist(r/musictheory)
Read every day! As much as you can. Even 15 minutes a day will make a big difference, but shoot for more. You wouldn’t expect to read English all that well if you didn’t read more than 15 minutes a day.
The big “challenge” with sight reading is digging up enough material at your level without bothering to work at finding it. If you’ve got the material at hand, it’s not hard to learn to sight read. You just crank through a bunch of stuff that’s not hard to read, and then you’re better at it. I can recommend this book from personal experience. This PDF is also helpful. For some fun melodic practice, check out The Session. But you want to make sure you can read multiple notes at once and some basic chords too. It’s no fun to freeze on stuff like that. You can also just go to the music store and find some books of reading material.
Make sure you always read with a metronome, and set it sloooowly enough that you can play the music easily. No speed is too slow if it let’s you play the music correctly, although if you need it at 30bpm you should look for some easier music when you get the chance. When you mess up, don’t stop. The most important thing in reading is to get tempo steady and the rhythm right, and not to lose your place. When you mangle three bars in a row, you still want to start the fourth bar on the right beat. The metronome will be extremely helpful in this.
The other important thing is not to re-read material or play very many songs you already know. After you finish reading a piece of music it’s good to go back and play whichever parts you messed up reading, but don’t go through the whole thing again unless it’s necessary to improve your technique. You’re not sight reading if you’ve read it before! Technique work is important too but be aware that it doesn’t count as reading time.
EDIT: But do scan (without playing) each piece of music before you read it, so you know where any repeats or tricky parts are, and what tempo you think you might need.