In an instructive video that I saw on Youtube by Molly Gebrian, a violist who is also a neuro-scientist, she emphasized that one should have a goal every time one picks up one's instrument to practice. This is probably something that music teachers should tell their students.
I'm aware of many weaknesses of mine as a musician, and I try to address them, not all at once, when I practice. Incidentally, my music guru, Arnie Lawrence, disliked the word "practice." He told us that we should play, not practice. In other words, there shouldn't be a difference between practice and performance - though he also hated the word "performance," as it suggests something artificial. A person who was performing was doing something slightly dishonest, at least as Arnie saw it. I don't see what verb you can use instead of "to perform," but maybe one should think of practice as performance.
Sometimes when I practice, I concentrate on my sound. I play long notes and intervals between them, trying to hear what I'm playing. How can you not hear what you're playing? It's easy, especially when you're reading music and concentrating on playing the right note, the one that's on the page. So what you hear is whether you played a G sharp when it's called for, whether you're playing the articulation and phrasing that the composer demands, but not the way you sound when you're playing. I hope that the attention I give to my sound, to the way I move from note to note, to the intonation, and so on, will carry over to my playing when I'm reading music.
I also work on memorizing music, playing by heart, transposing songs from key to key by ear. I hope to deepen my understanding of what I play. I consciously notice when an accidental appears in a song, when it moves momentarily from key to key, what the interval is from the end of a phrase to the beginning of the next one. I'm not good at remembering the chords that underlie the melodies I play, but I give them attention, too.
When I play the flute, which is not a transposing instrument, the written notes are the notes that are played. If a song is written in a certain key, those are the notes I have to memorize. But when I play the same song on a tenor saxophone or another instrument that's in B flat, I have to play it in a different key to produce the same audible notes. I often find it difficult to remember the original key of a song when I try to play it by heart on a different instrument. That's something I keep working on.
I also play duets with another flutist, and to prepare for our sessions I have to work in a different way. I wrote "work" and not "practice," because mastering the notes of the duets is work of a different kind from developing my sound. While I'm trying to master sixteenth-note runs and unusual figures, I also try to play with a good tone, but the focus is different.
Awareness and mindfulness, the goals of meditation, are not so much the goals of playing music as the basis of it. If you think too much about what you're playing you get in your own way. But if you don't think about it, you won't get anywhere. The difference between practice and performance is connected with the amount of thought in your playing. If you've thought enough while you're practicing, you shouldn't have to think much while your playing.
