keystring On the I IV V type of analysis. This is helpful if your music is rather diatonic. Like IV are the 4th, 6th, 8th note of a major scale in that key - in a minor key you could have IVm (or iv). But what if the music uses notes and chords not in that key (so, not diatonic)? Although very often we do have these, maybe with others interspersed: I (stuff, stuff) IV (other stuff) V - kind of like a rough framework of the general path of the music.
But then, even if your music does have that kind of structure, you have to already know them - you must be able to recognize what key the music is in (at that moment) and be able to recognize those principle chords.
I think you have to know Roman numeral analysis beyond I through V7. Being able to recognize secondary dominants, for example, will help explain notes not in the key signature.
keystring The pattern starts: Em7b5 (half diminished), E7b5, Eb7b5, Eb7 ...... new sequence: Gm7b5, G7b5, F#7b5, F#7 ... new sequence Bbm7b5.... etc.
Or the pattern is: half diminished chord (Em7b5), raise the 3rd so G to G# for the E7b5, do that same chord a semitone lower, turn it into a straight Dom7 (E7) by raising the 5th ..... do not resolve E7 normally (would be to an A) - instead start the whole cycle again starting a major 3rd higher.
This does not work for my brain. At all.