Kerri Chandler - “Mommy What's a Record”
All of the chord examples you've looked at so far have used only diatonic chords. But many types of music also use chords that are non-diatonic. Non-diatonic chords contain notes that aren't in the key.
What plays the chords?
The chords in this song are played by some type of synthesizer or sampler — an instrument that plays back audio recordings (or samples). More and more layers are added to the song as it progresses, but you're focusing on the string-like sounds that start at the beginning and play the chords throughout.
How do the chords work?
This song contains a progression of only three chords:
C minor 7, G minor 7, and A minor 7
These are all the same type and voicing of chord (minor seventh in root position). Chord progressions like this that consist of a single chord type that is copied and transposed are called parallel progressions (because the individual notes in the chords move the same direction and distance when the chords change).
This is an example of a non-diatonic progression because there is no single major or minor scale that contains these particular notes. In fact, it's a bit difficult to get a sense of what the key actually is; parallel chords often result in a "vague" or "floating" sound.
Parallel chords are commonly used in deep house and related styles.