They sound like maj7 chords, also m7 chords too. (This is just the first tune, I cba to explain the dominant 7 chords in the second one)
A maj7 chord is a standard major triad with the note one semitone below the root added to make a 5 note chord
Cmaj7: C, E, G, B (B is 1 semitone below C)
Do not mix up a maj7 chord with a dominant 7, also referred to as just plain 7 chord, they are different.
A m7 chord is a standard minor triad with the note two semitones below the root added..
C m7: C, Eb, G, Bb (Bb is 2 semitones below C)
When you use these kinds of chords in this kind of music to make this vibe, make sure they fit with the scale you are using:
E.g. In F major:
Cmaj7: is bad, because it contains a B, and F major scale does not use a B, it uses a Bb,
Bb maj7: is good, because all the notes (Bb, D, F, A) are in the F major scale.
The scales you want to use are the standard major scale and the natural minor scale, also called aeolian mode. You could consider the lydian scale or dorian scale, look them up.
Also, pay attention to which order you put the notes in in a chord. If you can, make every gap in the chord larger than two semitones, it will make the chord less clashy. Experiment with leaving one note out of the chord, or playing the notes in a different order (like C maj7: B, E, G, C)
