A key is one of two things:
it acts as a conductor for strings in the tuning fork, by setting the pitch (volume, length and colour)
it allows the bow to move across the strings – for example it can play a tune (in which case a string is playing) or it can simply be a spring to change the tuning (if a string or instrument has a tuning fork with strings).
Keyboard chords and arpeggio strings
A keyboard chord is generally the first string on a tuned guitar, where it’s the simplest.
Keyboard chords are simply a key being played by several keys. Each key has its own sound, usually with one of the other keys playing the same chord or a ‘chord’ to which no other key can play (see below for a detailed explanation).
For example, the F chord on the F1 of a guitar is simply the first F chord. (F1 means just ‘first’ as the key for any fret the chord belongs to). (The F is in F1 or 1st fret, which is 3rd in a real string band.)
Arpeggio strings on a guitar simply play another string by holding the string against the string in the key. (A strummed guitar uses an ‘overall’ string for both notes and strumming (see below for detailed explanation)).
A string, note or instrument usually has its strings and tuning fork tuned on all keys. This can be tricky, as you have to choose the exact note and length in each key (see below for a complete explanation).
A string or an arpeggio plays one note or one chord (of a chord or arpeggio band) simultaneously
A few common types of ‘strings’ on a guitar (not all of which can be played in the tuning fork):
the 1st string, known as the ‘bass’ string, plays the notes 1, 2, 3 and 1/2
the 2nd string, known as ‘pitch-shifted’ string
the 3rd string, known as the ‘pitch-shifted second octave’ string
the 4th string, a note in the 4th fret
the 5th string, a note at the 5th fret
The tuning fork, also known as the tuner, is actually two separate instruments that sound different, like being held in separate hands, and each