It all really depends on the kind of musician you want to be. If you are really into metal, than getting your rhythm guitar chops down and running your scales really is what you want to work out to match that intensity. If you love jazz, than transcribing, improvising over standards, and knowing every chord voicing is where your focus should be. I do know that for some people that isn't so simple, as we all have a wealth of different influences and interests.
With that being said, I feel there are some things that everyone should be able to do on the instrument. Regardless of style or preference; there are certain aspects to playing that I feel can benefit any player of any style. I am the type of player that loves it all. Where as I certainly veer towards some styles more than others, I love all styles of music and will always be a student of the instrument. Below is a list of things I practice all the time, and I feel are fundamental that all guitarists should work to be able to do. These are in no particular order.
1.
Triads - These really are the shapes to know on the instrument. Knowing each triad shape for every major and minor chord will really get you a long way. It is important to get out of playing large chord shapes all the time when you don't need too. If you are playing by yourself, fine. But, with other instruments involved knowing how to get to your triad shapes is really a great skill. Here are a few lessons I have done on this concept that will get you going.
Intro to Major Triads and Inversions Intro to Minor Triads 2.
Play all 12 Keys from One Spot - This was an exercise I learned from a guitar player I took lessons from named Tim Young. Essentially, you start on the Low E string and pick a note. From there you play up and down all 12 keys from that same spot. You do some major position shifting, but all in all you can get to all 12 keys from that one place. It takes some discipline, but regardless of how long it takes you work through it. It is not as challenging as you think.
3.
Know all the Notes - It is essential to know all the notes on the neck of your guitar. There is simply no way of getting around this. You can practice this so many ways, but I am a fan of the one note game where you simply pick a note and to a metronome play that note every where you can. Pretty straight forward.
4.
Sing What You Play - "Anything you can hum, you can play." I was told this by a teacher about 12 years ago. This is very true. Even if you are not a vocalist yourself, you really should work to match the pitch of any note you play. The deeper understanding you have of this, the easier it will be to get those ideas out of your heard and into people's ears, as well as giving you better skills at learning songs. Star singing!
5.
Soloing with Chord Tones - I have done a tutorial on this concept that will be on the site fairly soon. In short, you essentially only solo playing the notes of the chords you are playing over. Practicing this would either require you play with someone else, or record yourself and jam away. Either way, this concept sounds tedious but is very, very helpful in helping you sound more melodic while also bettering your concept of knowing the guitar neck among many other things.
There is my long winded response to this forum. Whoops! ;)
Douglas Showalter
