What We Found for Major
For any song, we have choices for how we voice the chords. The first option is the way a particular song is played. If a power chord tune, we use power chords. If an open string P1 song, we use those. If we are looking to copy a song, tone for tone, we go this route. Yet, we can always create any style of any song. We can play a punk version of a country ballad [use R5's for open string P1's], or an acoustic version of a rock tune [open string P1's for R5's]. Even when not style specific like this, we can choose from our chord catalog to create the chords which we see as symbols. As we expand our chord knowledge, this is a great way to accent or add to what someone else is playing. If they are playing P1 open string chords, we play something different. We don't interfere by playing the same voicings. An interesting point I'd like to get in the mix at this point is that a chord symbol is also a scale symbol. We can interpret a symbol as a chord [or chords] and a scale [or scales]. Just as we can simplify or elaborate a chord when we see a chord symbol, we can also interpret a symbol as a scale in different ways. The actual harmonic motion of a tune [its chord movement, which can be written as Roman numerals] is its wider structure. The key we play it in is its surface realization. The surface - the key - can change. This is a great way to put our chord catalog to work, while helping us to be more functional & flexible.
Here's an example of adding a new tone to a known scale to create a new scale...the E blues scale. In this instance, we are adding the B♭ [flat 5] to the E minor Pentatonic scale. When we do this, we create the E Blues scale. The B-flat acts as a passing tone when we are using it for soloing over E minor type progressions. And, this scale can be called E minor blues, since it has a flat-3rd. Train. Jam [this is a good one for the E minor 12 bar jam track]. Next, we will add different tones to the pentatonic shell to create different modes.
Chord train is a simple way to explore sound, make sonic judgments, create music, and bring cohesion to a group [without too much difficulty]. We also hear these sounds commonly used. Chord Train!