Level 3 is all about understanding the neck, & also applying understanding to advance more complex options.
A Level 3 player should be playing with others consistently & successfully, along multiple genres, and potentially multiple instruments, and able to adapt in multiple settings, & scenarios.
It's here, between Level 2 and Level 3 that the concepts, rules, and theory are concretized. A Level 3 player knows the rules of the game. This is the completion of the "rational" phase of development, where not only do your moves/theories work with you and your friends, but they can be applied "outside" your comfort zone also, and they work there too.
In Level 3, you should see 3 or more ways of doing any task. That allows for personal creativity and personal expression. You are creating and applying your unique “voice” as a musician.
A big part of seeing things 3 dimensionally is taking all the fundamental theory and experience you’ve gained, and being able to apply those moves away from the basic pocket - i.e. if something works here, it’ll work here and here too. On guitar this will include transposing, using a capo, the CAGED theory, mastering of scales. This yields expression of melody - making your instrument sing. Level 3 is about taking the core fundamentals of Level 2, having connected the dots (ideas, theory chords, etc) with lines (experience and time) and turning them now into objects. We are playing with these lines and connections and making "things" out of them. Confident, bold things.
Being a 3 dimensional player means you’re not only aware of yourself and your function, but the other functions of those you may be playing with as well. You see your piece of the pie contributing to the whole. Situational awareness is mastered in this level. The 3 dimensional aspect comes from your ability to express and contribute your voice with confidence, depth, and meaning. It's not about you anymore, it's about your part functioning in the overall picture.
Concepts become crystallized here, allowing for application of more complex explorations and delivery.
In Level 1 & 2, total focus and concentration is needed to complete immediate tasks. In Level 3, because of time, experience, and muscle memory, focus and ability is becoming second nature.
You should be learning to play comfortably in multiple styles and roles. Music understanding can easily apply to other instruments, and other instruments are comfortably explored.
In Rhythm, a level 3 player can think into 1/16th notes (or beyond) with ease. This is a complex place within the beat. Your mind doesn’t just think in basic patterns - keeping up, but within each moment, more complex rhythm patterns can be expressed. Words like groove, space, and funk, etc can be used (when applicable).
This is the most rewarding level, as you should be contributing on a bigger scale - playing confidently and regularly in a band, for church, for others, etc.
As an 18 to 30-something-year-old sees the world, a lower Level 3 musician sees his instrument/music. You’re going "out into the world," and figuring out who you are and what your contribution to others is. You’ve spent all those years and all that experience behind the scenes working on your craft, understanding and processing the world (or your instrument), and now you are planting your feet within the bigger picture. You don’t know everything (as many people this age think they do), but you have some miles behind you, and something to contribute.
A musician in the upper end of Level 3 will be living their "power years," meaning, you're contributing at the highest level of your life, and doing so successfully. Consider a person in their 40's and 50's, developmentally. They're seeing the fruit of their years of labor and diligence. They're engaging with the world at the height of their life. Contrast that to the musician (of any age) successfully and consistently contributing their craft for themselves and others at the highest potential of their life. This is where it's all happening - the "work" you put in now is for the demand coming from your ability and talent. This is where most of the accomplishments related to your current work are going to come. All the tools you'll need are in your hands, and there's a high demand for your talent and ability. Often there's a sense of "cruising" at this upper end of Level 3. As a Level 3 musician, you'll have anchored yourself within society, in some form or fashion - uniquely to you. Your "voice" is confident and carries weight, especially in the upper end of Level 3. People tend to listen when you talk, when you play.
Are we having fun yet?
Because Level 3 isn't about you as much any more, but about your contribution and relation to others, here are some things that are necessary to be successful in Level 3: on the social aspect, can people depend on you? Do you carry your weight? Do you prepare? Are you a decent human being that can get along with others? Or, do you dominate the sound spectrum, making your piece of the pie too big, or do you trust the others in the group to carry their part? A level 3 player (or person) understands balance and harmony with others both while playing and in social settings.
Do you have the tools and knowledge you need to be successful mentally, experientially, instrumentally, gear-wise, socially?
A level 3 player will have been playing consistently for 10-15 years or more.
Lower end of Level 3 represents someone in their 20's/30's cognitively/developmentally.
Upper end represents "power years" of 40's and 50's.
3,500-10,000 hours put in.