Visualizing the piano keyboard while meditating is a good mental exercise. Middle C on the piano is C3, with C1 being the first key on the left of the keyboard. The guitar notes start at E2 on the keyboard and go up to C#5, on a standard 21 fret guitar neck. i have a 24 fret neck guitar, so on that it would go up to E5. On the bass guitar, it starts at E2, which is one octave lower than the guitar. It goes up to C4 on a 21 fret bass. Getting familiar with the range of the guitar and the bass within the piano keyboard makes you think more like a Symphony Conductor and gives you a broader view of the musical spectrum. Understanding the keyboard is done by breaking it up into the repeating patterns stating at C1 , Using this meditative technique while i am doing something like waiting in line or lying on the bed is a good brain exercise and a good use of time otherwise wasted. It is part of my goal in learning to sight read music. It is good for Composing as well. If you think of it as an App in your brain that it you can turn on, instead of automatically going to your phone.