Even though it is somewhat expected of us, as professional classical musicians, to perform from memory, we could do it with sheet music in front of us.
But, should we ?
I will share my personal experience as a performer and a piano educator here.
I could perform using the score, and I do that sometimes, especially when I accompany or play with another instrumentalist or a singer, but in all my solo performances I perform from memory.
Why ?
I play much better, much more expressive, if I play from memory. I can focus on the sound only, instead of dividing my focus to also looking at the score, flipping the pages, etc.
I prefer to go even further and play some parts or even whole pieces with closed eyes. It is something I started to do recently more and more and something I started to be very comfortable doing.
When I do that, shutting out all other senses and having much less distractions, the only sensation left is sound, and then music starts to sound differently to me, sometimes slightly, but sometimes substantially and surprisingly different. I could discover whole parts that I missed to give an importance to, or depth to. I can notice nuances I need to work on or express differently, nuances I usually don't notice with my eyes open, focused on the score, and/or on the keyboard, and even on what is going on around me.
And as I do that, I can let music take the lead, to take me wherever it wants, which is usually far away from my piano, leaving this world behind ...
So yes, performing from the score is not exactly frowned upon, and it is even necessary if we need to perform a piece we had only a few days to learn, but playing from memory allows us freedom to focus on music only, and results in deepening and better quality of our performances.
As a piano educator, I encourage my students to learn how to memorise and perform from memory, however to practise with a score in front of them, to study and re-study it over and over again ...... to search for and discover details they might have missed before.
What is your experience ? Feel free to let me know in the comment.
More about why professional classical musicians perform from memory read below:
I am in awe with how many pieces you and other pianists play from memory and how comfortable you are with that.