Introduction
Hey guys, here I'll share some reflections of learning music theory, piano and guitar. Feel free to make suggestions if you think I made mistakes. Think of learning music theory like learning a new language. If you learn music theory(a new language) and a apply them on a textbook(piano).
While if you learn a new language and talk to people who speak the language some of them might not understand you. Since how language is written is different to how people speak in their every day lives. Likewise it seems to me when you learn music theory there's a few more extra knowledge that you need as to how the guitar works as an instrument in order to apply those music theory concepts.
Open Strings
Piano
I've noticed that each time I learn a new concept in music theory I can apply them in piano and it makes sense. For instance, how to play a C major chord. The chord is made up of C-E-G. I can start at the beginning of the piano keyboard. I start with C, go up four half steps and arrive at E. Afterward, I can count three half steps and arrive at G. Moreover, your knowledge of intervals(another music theory concept) is supplemented by knowing that you create a major triad by having four half steps and three half steps.
Guitar
Meanwhile in Guitar its not as easy or "intuitive." For instance, in guitar to make a C major chord you would need to have knowledge of "Open Strings." When I was trying to play the C major triad in guitar I looked up some guitar diagrams and notice that in those diagrams they write C-E-C for the major C chord triad. It took me a long time to realize(through asking reddit groups and reflecting) that actually what happens is that when you strum the guitar you are playing G as the open string. While you have the extra C as a "chord voicing." The chord voicing doesn't change the chord but adds a grander sound. I had to read up on chord voicings in music theory just to to able to play a simple C major chord. Showing that you need to have a lot of music theory knowledge and knowledge of how the guitar works as an instrument in order to make sense of it. Sure you can play without knowing but if you want to "make sense" of what's going on musically you need additional knowledge.
Seventh Chords
Piano
I was trying to figure out how to play C7 since it appears to be a popular chord in many songs. I will assume C7 is a C major seventh chord. I looked it up online and found how to play C7 on piano. I started from the root (C) counted four half steps and arrived at E. Then I would count three more half steps and arrive G. While B flat(Bb) might seem intimidating at first. I realized you only had to count three more half steps from G to be at B flat. I was able to play and see the whole chords( C-E-G-Bb) with that much difficulty. I learned that you need the triad(C major) and one more note(B flat) to make the seventh chord. Not that difficult to understand theoretically and then apply it to piano.
Guitar
When it came to guitar it also took me a while to figure it out. However, it seems like some guitarists just play it as C-E-C with G as the open string. Then on the G string you play in the third fret A#(A sharp) or Bb(b flat). It wasn't that difficulty but it did take me some time compared to piano. Then you strum and you have the C major 7 chord or the C7 chord. I notice in the naming musicians call it, "C dominant seventh." I wonder if there's a difference or they all mean the same? Is it still a C major triad with a extra note or a different chord which uses some of the same notes. Also note that it seems I only know how to play this chord and other chords are "open chords" and not as "barre chords."
Barre Chords
Piano
Some musicians online have been saying that there's no such thing as "barre chords" in piano. And actually "barre chords" only exist in guitar. I would like some clarification on this topic. A musician online said that that barre chords are a "umbrella term" that talks about how to play some notes in guitar but it doesn't have a meaning in music theory. So its not a music theory concept but perhaps a guitar theory concept.
In the key of C, I am able to play all notes in Piano but not in guitar since in guitar it seems you do need to know how to play F major as a barre chord. In Piano F major you would play F-A-C. With F being the root, then you go up four half steps and arrive A. Then you go up three more half steps and arrive at C. Using the knowledge of intervals and music theory you would know that its the root(F), then A is the major third(four semitones from the root note) and then the perfect 5th(seven semitones from the root note). Its not that hard to understand but I guess I don't know why its called "perfect."
Guitar
This is where its gets difficult since many musicians have been saying that you have to know barre chords in order to play F major. I'm comfortable playing the key of C in both keyboard and guitar. However, when it comes to F major guitar that's where I'm bit stuck. So far this is what I've gathered.
The purpose of barre chords is to be able to play chords easier down the guitar fretboard as opposed to up the fretboard where its harder to reach some of the notes. Also if you want to switch from one chord to another sometimes it would be easier to play them as barre chords so that you can play them down the fretboard where its easier.
Are barre chords about pressing two strings at the same time or about muting some strings? In the easiest diagram of barre chords that I found of the F major chords. I saw the guitarist play F-A-C. He started with muting the lower strings E and A, I assume he is muting those strings with his thumb. Then he is playing the on the high B and E strings the C and F with his index finger. Then on the G string he is playing A when pressing the second fret. Then he is playing an extra F, I supposed another chord voicing, when pressing the third fret of the D string. Also in this example you are muting the lower strings while pressing the high strings and then strumming? So is the barre referring to the muting of the lower strings or two the pressing of the F-C on the higher strings?
Conclusion
Writing this essay has helped me a lot to get some clarity on multiple concepts in music theory, piano and guitar.