Favourite background/instrumental music from k-dramas?

I am now presenting a masterpiece of BGMs in the modern genre.
Here we enter the realm of perfection.
Save Me.
The team of musicians is composed of : Jung Se Rin, Lee Yoon Ji, Lee Roo Ri, Joo In Ro, Noh Yoo Rim, Goo Bon Choon, Kim Hyun Do, Kim Jun Seok.
Maybe one name is missing, or one person is too many in this list. If I mention the list of musicians, it's because it's approximately the same on the dramas W two worlds, Signal, Memories of the Alhambra.
And all four records are of incredible quality. It's hard to say which one is the best, but I'll put them in this order: W, Save Me, Memories of the Alhambra, Signal.
https://wiki.d-addicts.com/Save_Me_(OCN)_OST
https://www.youtube.com/watch?v=8VvSqtXL8jI&list=PL2GMtjIf0bZD727gOsMpRKmoca8hITYq6

The music on "Save Me" is so good, that paradoxically, I found the drama disappointing. Maybe because I had made the mistake of listening to the music before seeing the drama, and my imagination was too excited.
The main problem is choosing what to post here.

Title (Opening Credit)

This title uses a song that you don't hear once in the drama. Which is a shame, because it's also one of the most beautiful drama songs I know.
Hwayobi OST Part 5

The end in particular, from 2:55.

Good And Bad

My favorite BGM. Ambient, dark drone. Shivering, scary, freezing, drifting towards mental illness and fear. This track is emblematic of the whole record, because it is mainly this kind of atmosphere that we find in the drama and on the majority of the tracks of the background music.

The Last Whisper

My favorite song tied. Difficult to find on the internet because on the Cd n°2. I didn't hear it once during the drama. But if you've spotted a scene that uses it, let me know.
After the thrilling intro, the song is minimalist, but with the exact right sound. Only two sets of three notes of music. The first set is an easily listenable sequel. The second series repeats the same rif, but with strongly destabilizing notes suggesting a mental disorder.

Hidden Tears
https://www.youtube.com/watch?v=4V0i-lL-OGU
A religious atmosphere, with some very heavy, resonant and deep box strokes.

Promise
https://www.youtube.com/watch?v=kX3ygiMZqiY
A pop-rock music with a good rif on the saturated guitar. A song easy to remember.

Bitter Reality
https://www.youtube.com/watch?v=vCo2Cv3rwso
Atmosphere of disturbing mystery. Waiting situation. Halfway through, a well-defined rif at the piano.

Exorcism
https://www.youtube.com/watch?v=l7N6pldlR5g
A brutal piece, depicting people possessed. Difficult to choose this track rather than another, because there are several other action tracks, with drum sounds, combined with disturbing ambiences.

Two Faces
https://www.youtube.com/watch?v=h42vfJVWwWo
Once past the shimmering intro, a cold and heavy atmosphere that drifts towards psychological instability. Then a slightly more optimistic ending.

Guseonwon
https://www.youtube.com/watch?v=OsHVLrmfsSY
A piece I particularly like with some catchy piano riffs.
Illustrates a plot in progress, a risky plan.

Saved Devil
https://www.youtube.com/watch?v=syQoM0h2zsc
A lot of work on the sound. Difficult to choose this piece among others of the same kind. I can't say for sure that it's the best.

Heathen
https://www.youtube.com/watch?v=kNJhAEipqtQ
I love this piece too. A sectarian, glittering sound at first. Superb, it gives this track its uniqueness.

Worship Of Evil
https://www.youtube.com/watch?v=_cmBcqb3fFk
Okay, I really like this piece, too. It's got a great intro. Strident, barrel-crushing, creepy, humming sounds.

Misplaced Start
https://www.youtube.com/watch?v=Y7xHwn7tgFE
Another beautiful piece... A distant and nostalgic delay guitar.
From 01:00, the song leaves its stagnant phase and becomes harmonic, downright beautiful.

무지군의 비밀
https://www.youtube.com/watch?v=_jTCjd0AfQ4
Very dark atmosphere. Sounds of cold puffs. Resonant heavy blows, scrapings, a little bit of everything about scary sounds or even ambiences. It's quite varied. Could reflect the mental state of someone who has become permanently alienated.

구원받은 악마
https://www.youtube.com/watch?v=zxijhETHps0
Slightly pop, no rhythm. A slightly simplistic song that is interesting for its delay+reverb guitar sounds.

위장된 구원
https://www.youtube.com/watch?v=Ez2Cp6pxuAc
Heavy and powerful synthetics, mental helmet effect. Very deaf heartbeat. Distant bells.

꼭꼭 숨어라
https://www.youtube.com/watch?v=bHQwOTpx9Sw
A warm and emotional piano piece. Warm or sad. Either way, it's one of the rare pieces that is slightly more optimistic and doesn't freak you out.

어긋난 시작
https://www.youtube.com/watch?v=Z5oY4vCzqnU
Very gloomy. Built on heavy sounds, strikes, metal, rather than on synth strings. Squeaks a little too. Very good ending.

어깨 피라!
https://www.youtube.com/watch?v=4g3tvXn1bhs
Beautiful. A celestial and angelic flight. Or maybe you're dead but you don't know it yet...

I have to stop here with the background music. I apologize for all the other music that deserved to be in this list, and that I didn't link. Just listen to the playlist.
The problem is that you have to get to the songs now. And again, Save Me's OST is a masterpiece. Already the previously mentioned song.
Here are the other songs of the drama, most of which have an instrumental version used as BGM.

INKII - "Out Of The World"

I don't usually like songs that are a bit too powerful and noisy in this genre. But this is musically very good. The singer seems lost and distant on the verse. Adding a lot of reverb to the voice.

INKII - "I Am"

Same sound for the vocals, on a slightly softer song. More harmonious.

THE VANE - "Illusion"

A very rocky chorus.

Jung Cha Sik - Sandy Wind
https://www.youtube.com/watch?v=qTbVAAWZf9E
This song is ugly. It's a lament. The style is reminiscent of '80s dark-wave, Bauhaus-type artists. So the song is ugly, but it's interesting at the same time. Around 2:00, which sounds like a good chorus. I like it, it's original, with a good sound, double bass + piano.

now I'm in the mood to post other "dark" music. I liked the music used in Priest & Black but they didn't release them :/

this one is chilling. (the vocals) there's supposed to be 45 BGM for Lovely Horribly but I don't know why they made their videos private, I only uploaded a few of them for my own channel.

this one is fun to listen to:

and other ones:

 W two worlds Season 2:

The music you just posted on "Black" makes me want to see the drama. ;-)

that music is from the scene in beginning of ep 1. It's a shame they didn't release an OST for their music.

I'm waiting for Rugal's BGM to be released, a few of them reminds me of TLE - I wonder if it's the same music composer?

posting some of my favourites from The World of the Married & The King: Eternal Monarch:

there's a song that wasn't released, it played in the beginning of ep 1:

this one is short but I would've liked to hear a longer version:

also I like the instrumental version of Gravity (without the singing in it) it sounded cool when it played at the end of ep 11 and I just don't really like the melody of the chorus part??

For the extracuricular piece, I don't think it really looks like Save Me.

World of the maried: I haven't had time to listen to the whole BGM record yet, but I remember that in the drama, some of them were very good for maintaining suspense and tension.
"The World where everything is perfect" is really a key theme, easy to remember!

On rugal, I might need to see the drama. I really like the title "Like a Yip Man" with the slap bass. Rather the music for itself, because often this kind of track doesn't go very well in dramas.
"An absurd dance" is original and surprising.

I'll be back soon with a detailed BGM record!

 W two worlds Season 2:

- I spotted the musicians 박세준 (Kim Min Ji) and 우지훈 (Woo Ji Hoon) on the record. No wonder the BGMs are so good. These musicians signed compositions on the soundtrack of Extraordinary You. The drama was bad, but Extraordinary BGM. I haven't made a list of the musicians on 365 yet, but it will be worth it.

Park Se Jun was one of the composers for Rugal, Extraordinary You and My Strange Hero. When I watched EY I thought one of the BGM had a similar vibe to MSH (forgot the names of those 2 songs but I might edit this post later), was surprised I guessed it right that it was the same music composer! I agree the drama was a letdown, it was actually fun to watch in the beginning but then I got bored halfway. It's funny even though I dislike some dramas but the bgm is still nice to listen to. I'm still trying to watch 365: Repeat the Year. I finished Extracurricular but didn't really get the hype over it. Meanwhile I'm enjoying another makjang Come! Jang Bo Ri (same writer of TLE) :D

 Sunset:

funny thing happened to me today when I heard a song on the radio at the mall (Radioactive - Imagine Dragons) the intro sort of reminded me of Extracurricular? I see a few others thought the same too on YT comments but this is coming from someone who doesn't listen to this band's music... 

Pop, rock, kpop, OST songs, etc, use a limited number of harmonic progressions, often a 4-bar grid, with 1 to 4 chords, or often basic chords. This makes these musics most of the time boring, except when the arrangement gives them originality.
Even without wanting to specifically copy another song, it is quite normal that a musician sometimes draws the same chord grid, or that there are similarities. This also happens with music for films or series. What makes a song unique and its quality is difficult to define.

For the track you're quoting, I just listened to it here:
https://youtu.be/ktvTqknDobU?t=70
At 01:10, listen to the tune of the song (melody/harmony).
You have something similar in this Save Me OST:
https://youtu.be/Skc9y_K3J4k?t=55
At 00:55, looking like, isn't it?
The two titles also have many other similarities.
This is not necessarily a plagiarism, just a reminiscence of the composer, or a coincidence.
On the title of Save Me, the chorus is better defined for example. The melody is followed without interruption by lower notes from time to time, as is the case on the other piece.

When the Camellia Blooms

Smell Like Something Fishy - Park Jung Hwan

OMG - Park Jung Hwan

Bloom

너 눈깔이 왜 또 이랴 - Various Artists

향미야 너 진짜 왜이래 - Gaemi

Full OST playlist