(Content, in part, adapted from a public domain writeup I did for a wiki: http://library.sound-club.org/wiki/Casio_Chord)
Casio Chord is Casio's simplified system for playing chords on the accompaniment keys (usually the first 18 keys on the keyboard) of their keyboards. Most Casio keyboards with accompaniment keys (in Casio Chord or fingered chord mode, these keys produce (usually) a bass sound and an organ-like sound, rather than the currently-selected patch) have a simple "fingered" mode, where the player simply fingers chords as normal, but Casio decided to simplify the process of fingering common chords (triads and seventh chords) for their non-professional target market.
Chances are, if you have purchased a home-market keyboard in recent history, or ever received anything for Christmas in the 1980s, you have used a keyboard with the Casio Chord feature.
When Casio Chord mode is selected, pressing one accompaniment key elicits a major chord in that key. While holding this key:
- Pressing any one key to the right of it changes the chord to a minor chord,
- Any two keys to the right produce a major seventh chord, and
- Pressing any three keys to the right produces a minor seventh chord.
Additionally, operating the Casio Chord feature whilst a rhythm is playing (for those models having a built-in drum machine of some kind) generally causes an obligato melody and bass line fitting that rhythm to be produced, in the key selected by Casio Chord.
Some models (notably the popular Casio SK-1) also feature "variation keys", allowing for complex chords to be played with two keys (i.e. F# + sus4 variation key for F#sus4).
Use of Casio Chord makes fingering significantly less complicated, making complex harmony more accessible to J. Average McSound until such time as they become more sure of themself on the keyboard — the experience that really helped me figure out that music is a grand old time and I wanted to learn it was the first time I played an original improvised melody with chord backing, without any real experience with keyboarded instruments. Ever had one of those epiphanic moments of sudden realization which cause you to laugh even though nothing is actually funny?