Major to minor chord turnaround.

Open_G Frets: 257
19 Sep, 2024
Ok so I don’t really know if this is the right term for this but I’ve found I always love it in songs when they have a chord pattern that includes a change from say a C major chord to a C minor- usually next to each other within the song. 

Examples being found in Radiohead’s Creep, More than words, or Eva Cassidy’s Somewhere over the rainbow. Just to name three. 

I always dabble a bit with songwriting and never  find myself in a place to use it. I also realised I have no idea within my limited understanding of theory, how this even fits into the basics keys and what should and shouldn’t work together. 

Why does this work and how? It’s got me flummoxed!!!
Comments
viz Frets: 11208
19 Sep, 2024
Yep, that's a IV - iv progression. Lovely. Also found in Don't Look Back in Anger - especially the violins at the end, 4:20

https://www.youtube.com/watch?v=r8OipmKFDeM

An alternative, which sounds a bit less deliciously smoochy but is used in jazz a lot, is to go from the IV to the bVII (13) chord. 
HAL9000 Frets: 10264
20 Sep, 2024
The famous one is Richard Strauss’s Also Sprach Zarathustra (the Apollo space program music). Starts with the C G C notes followed by that dramatic C to Cm chord change.

See also Lucy In The Sky With Diamonds by The Beatles - A A7 D Dm.
I think In My Life by The Beatles has a C major to C minor chord change too.
Open_G Frets: 257
20 Sep, 2024
So 4th to minor 4th. Going to have a play with this and see if I can incorporate it to something. 
relic245 Frets: 1163
21 Sep, 2024
The major to minor 4 is a favourite of Elton John.

Goodbye yellow brick road 
Rocket man 
Sorry seems to be the hardest word.

I'm pretty sure there are others too.

It's a lovely dramatic change.

Od course it's also in everytime we say goodbye - even the lyrics tell you that it's happening
HAL9000 Frets: 10264
21 Sep, 2024
relic245 said:

… it's also in everytime we say goodbye - even the lyrics tell you that it's happening
I can’t believe i didn’t think of that one. Probably the most effective use ever. 

There's no love song finer
But how strange the change
From major to minor
Ev’ry time we say goodbye

One of my favourite songs that does this is Underwear by Pulp.

The verse has a great I-III-IV-iv thing going on and then the chorus starts with IV-iv, it really is a great hook.

https://youtu.be/0gE__8xuwoo?si=HTNB_9G__Ph2R41T
Also to try and answer the OP's question - I think a lot of people would describe this trick as a Modal Interchange.

"the internet" can explain this better than I can, but the basic idea is that if you're in the key of G major, say, then borrowing chords from G minor can sound awesome.