Why does this progression make sense?

Hey guys, this is my first post on this forum.
Last night we were playing songs at a party with some friends, and we tried to pick up the progression by ear… but there was a chord we weren’t able to get. Eventually we searched for the chords online, and this is the progression:

I - ii - iii - vi - II - IV - V7 - I

My question is… why does the II chord make sense? Its not acting as a functional secondary dominant…

Thanks!

The II chord provides very smooth and chromatic voice leading into the IV chord and therefore functions as an extension of the predominant.

I’ll reiterate further->

In the key of C (given your example)

Cmajor > dminor > eminor > aminor > Dmajor > Fmajor
I - ii - iii - iv - II - IV

Change the scale to a different relative mode. What is relative to Cmajor? Aminor!

Cmajor > dminor > eminor > aminor > Dmajor > Fmajor
III - iv - v - i - IV - VI

If you look at it in the context of aminor, you can see the Dmajor is being borrowed from the dorian mode. This is very very very common!

Thanks guys! Makes sense both ways.
:smile: