Remember to single out sections of a song or piece that are particularly difficult, and repeat them over and over. Practice with a metronome, sing the melodies, listen to the tone, pitch, and volume of the sounds you are producing with your instrument, and play confidently. Eventually, try to commit the song or piece to memory so that you can express the emotion of the music. For example, if the song is happy, melancholy, or sad, you won't be able to express that to its fullest potential if you are still reading the notes off of the page. The notes, the melody, the phrases, have to be ingrained within you, and flow out of you through your voice or fingers. Your attention cannot be divided between worrying about what note comes next, what dynamics should occur, or thinking "oh no, here comes that difficult measure". The audience will appreciate the time and energy you put into each song, especially if it is played with enthusiasm, focus, expressiveness, and energy.
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