It's the fastest way to improve.
Recording your practice sessions is an effective way to accelerate your improvement. Here's why:
Have you ever tried to do homework and watch TV at the same time? Odds are you end up not really paying attention to the show and you do a poor job on your homework. You get much better results if you focus on just one thing. The same is true for practicing music. Working through a new piece of music or practicing a difficult passage requires a lot of mental energy. Our mind is filled with thoughts like "Remember, more air on this note" or "Think subdivisions to keep steady." Paying attention to the "doing" aspect means you can't really pay attention to how you sound. Or, if you do, then you are taking away focus on developing or improving a habit. Recording your practice session frees up your mind to focus on doing one thing at a time, which means you'll do it more effectively.
"A photograph doesn't lie." Have you heard that saying before? It's less true in today's world of photoshop, but the idea is that a photograph captures a moment in time without our personal experiences clouding our interpretation. You might have experienced this when retelling a story with a friend and you swear something happened one way, and they swear the opposite. Our point of view, emotions, and physical feelings can all cloud how we see or hear something. For example, if I am feeling dehydrated, then I am more likely to describe my sound as "tight" or "thin" because that is how my lips feel. The truth of how I sound might be something very different.
Recording yourself removes those other thoughts and allows you to focus on what really matters; how you sound. This is especially effective if you can give yourself some time between when you record and when you listen back. Allow yourself to forget how you felt when playing.
Inspiration is always described as coming in a flash. It comes out of nowhere and the disappears just as quickly. These moments come from a unique combination of elements that are hard to recreate. They make perfect sense in the moment, but days later, these ideas somehow don't have the same resonance. It is important to capture your ideas as they happen. By recording your practice session, you can explain these moments in great detail as they occur so that later, you can recall the insight.
Have you ever felt sick right until you walked into the doctor's office? Or have issues with your car until it rolls into the mechanics office? Life has a funny way of giving us problems until we want to show them to the person with the expertise to fix them. This is true for our playing, too. Sometimes we might have issues that we want our lesson teacher's opinion on, but we cannot explain or recreate it when we're in the lesson. A powerful teachable moment has been lost. When you record your practice, you capture these moments, which makes it easier to (1) diagnose and (2) highlight to your teacher.
When you have a consistent problem, listen back and ask yourself the following questions:
If recording your practice sessions is so valuable for improving, then why is it that all musicians don't do it? There are probably many reasons, but one that I hear from my own students is that they get nervous.
Do you get nervous in performance? Yes. Do you get nervous in auditions? Absolutely. The only way to reduce that is to practice getting nervous. When you force yourself to get nervous, you get used to how it feels and what you need to do to overcome those nerves. With that in mind, if hitting the record button makes you nervous, then that is a low-risk way to begin to work on that problem.
The journey to master a musical instrument is not an easy one. Some days are fun, and some days are frustrating. It's common for us to feel stuck in our progress and begin to lose motivation. That is because progress comes slowly and in small doses and it can be hard to notice improvement. However, if you listen to a recording of yourself from last month or last year, you might notice dramatic improvement in your playing. Listening back can remind you how far your hard work has taken you and encourage you to continue.
Whatever your reason for recording your practice sessions, it is important to always write down your learnings. Two of the major reasons to write down your insights are (1) Writing things down actives more of your brain, causing you to remember them more easily. (2) Listening to an entire practice session again can take a lot of time. Jotting down the most important aspects in your practice journal will allow you to quickly skim and remember what happened. Personally, I like to also jot down time stamps so that if I want to go back and listen, I know exactly when to fast forward to.