A chord is a combination of three (or more) notes.
According to the above definition, the minimum requirement for a sound to be named “chord”, is to include three notes that are played simultaneously. This definition is valid for any instrument, from the mandolin to the violin and the piano.
Focusing on the mandolin, to play a chord you need to use at least three different but adjacent string pairs, as you can not play two notes on the same string (at least the last time I checked, ha).
Now, to play a mandolin chord you may have to use all four fingers of the left hand and this is a 4-finger or “difficult” chord. Here is an example:
You may also get lucky and use less fingers and this becomes an “easy” chord. Here is an example of an easy C major mandolin chord (1st inversion):
But are there any exceptions or variations to this defintion? Of course! Here you are:
Why limit yourself to three notes? Depending on the instrument you are playing, chords can have more notes, in fact you can include in a chord as many notes as the strings of the instrument.
- Mandolin Chords – may include up to 4 notes and then you are playing “difficult” mandolin chords.
- Guitar Chords – may include up to 6 notes.
- Piano Chords – may include up to 10 notes, i.e. equal to the number of your fingers!
You can argue that two notes do not constitute a chord but just an interval. And you may be right!
On the other hand, two notes played simultaneously definitely imply a chord (but which?), so two-note chords, or dyads have been used extensively in music.
These notes in a chord need not actually be played together: arpeggios (broken chords) may, for many practical and theoretical purposes, constitute chords.
Take the violin for example. Playing violin chords is tricky as due to the bow, a violinist can only play simultaneously only up to 2 strings, i.e. a chord can have only two notes.
So, a violinist instead can play three or more notes in sequence, and we call this arpeggio.
In fact all instruments support this technique, so we have mandolin arpeggios, guitar arpeggios etc.