So, im leaning the songs of this uruguayan artist called El Principe, and trying to get what harmonic devices he uses commonly in his songs.

While learning Detras de ti, i was analyzing the chord progression and... Its kinda functional? Lots of ii-V-I, but there are some weird chords in there like a i-io7-i or a V-I-vi-v-VI7 on the instrumental part.

My question is... is there a "functional justification" for those chords? How would you analyze it?

  
This is the structure i got so far...

Intro: (starts in Db major)  
| ii | V | I | vi | v | VI7 | ii | biio | I | vi | viiø7 | III7 | vi | ii | % | III |

*(V-i of ii?)               (mod via ii-V-i to relative minor)*  
*(v minor?)        (TriSub)*

  
Verse: (now in Bb minor)

| i | v | bVI | % | iv | bVII7 | bIII | i | ii | V | i | iv |

*(ii-V-I of relative maj)             (sometimes is IV major???)*

  
| i | v | bVI | % | iv | bVII7 | bIII | i | bvii | bIII7 | bVI | % |

*(ii-V-I of VI)*



Chorus: (still in relative minor i guess??)

  
| i | io7 | i | % | iv | bVII7 | bIII | % | 

 *(io7????)           (ii-V-I of VI)*



  


a little help analyzing this song?