The issue here in this thread is probably the need of a course that teaches people properly ... at somebody's preferred rate. And not books that beat around the bush or just goes over peoples heads, and is vague, and no good examples. A course that starts at the beginning and does not have disconnects between sections, and teaches everybody in a coherent fashion.
But in this thread ... somebody mentions transpose. And somebody else correctly pointed out that we're not dealing with transpose here. Transpose is taking every single note of a piece ... and applying the same offset ... eg. shift each note by +3 semi-tones.
Yes ... with the relative minor ... it is an approach toward adding interest or substance to particular music. And somebody mentioned 'key change'. And some use a 'fancy' word ... aka 'modulation' - which is a word (apart from 'action') that was probably hijacked from the dictionary by some hijacker in the past.
In any case ... we'll just use that word. Look up 'modulation technique mangold project youtube'
Also ... key change will generally involve known methods, which can be (are) taught or learned. And when playing within a 'key' ... people often teach what to look for ... or to listen out for, such as they teach people about many pieces of music starts with the root note of the 'key' (aka the tonic or whatever we want to call it) and usually ends with the root. But not always ... which is what they teach too.
But lets say that somebody does successfully 'modulate' to a new key ... such as transitioning from C major to A minor. Once that transition is made ..... the 'mood' in the minor key will be perceptively (noticeably) different ... relative to the major key that was initially being used.
And to transition back to the first 'mood' that sounds more positive and cheery etc (the 'major' key) ... it usually requires a method or sequence of notes to get there ... a method ... a formula ... to get back to the 'major' key.
And ... as mentioned before ... check that link below, and go to the very last audio example there.
And - transition from one 'key' to another one --- is not always straight forward. Due to some theory - such as circle of fifths/fourths etc -- people learning key changing (or 'modulation' as some call it) is easier or more convenient to do for closely - or closer related 'keys' (relative to the initial 'key').
What I think is important is ... when asking questions about the theory/techniques, definitely avoid dishing out insults on the music theory. Because -- asking about and attacking the theory simultaneously - when it didn't attack us to begin with - is a sign of something. Whatever that something is.
