Chord is a concept in music theory, which refers to a group of sounds with a certain interval relationship. When three or more tones are combined vertically according to the superposition of thirds, they become chords. There are usually triads (three-note chords), seventh chords (four-note chords), thirteenth chords, etc. Chords are also called polyphony, which refers to the simultaneous pronunciation of multiple sound sources. For example, if a string quartet is a quartet, it requires at least sixteen sound sources to be perfectly expressed; an octet requires thirty-two sound sources, which means that a multi-chord mobile phone can simulate the performance of a polyphony, so , talking about "polyphonic ringtones" is not completely unreasonable. Polyphonic ringtones are far more beautiful than tinkling single-tone ringtones. Their sounds are fuller and mellower, giving people a beautiful listening experience. Major triad: The root and third notes are major thirds, and the third and fifth notes are minor thirds. They are represented by the capital English letter name of the root note, such as DO, MI, SOL. The chords are represented by C, FA, LA, DO. Chords are represented by F, MI flats, SOL, and SI flats are represented by Eb, FA sharps, LA sharps, and DOL sharps are represented by F#. Minor triad: The root and third notes are minor thirds, and the third and fifth notes are major thirds. They are represented by the capital English letter name of the root note plus a lowercase m. For example, RE, FA, LA chords are represented by Dm, MI, SOL. , SI chords are represented by Em, MI flat, SOL flat, SI flat are represented by Ebm. Augmented triad: The root and third notes, the third and fifth notes are all major thirds, use the capital English letter name of the root note plus aug or add a " ". For example, DO, MI, SOL sharp chords are expressed as Caug or C, FA, LA, DO sharp chords are expressed as Faug or F. Diminished triad: the root and third notes, the third and fifth notes are all minor thirds, use the capital English letter name of the root note plus dim or a "-". For example, RE, FA, LA flat are expressed as Ddim or D-, DO sharp, MI, SOL are expressed as #Cdim or #C-. Major and minor seventh chords: Add a minor third to the major triad, just use the capital English letter name of the root note plus "7", such as SOL, SI, RE, FA chords are represented by G7, LA, S sharp DOL , MI, SOL are represented by A7. Major seventh chord: Based on the major triad and adding a major third, it is represented by the capital English letter name of the root note plus Maj7, such as DO, MI, SOL, SI chords are represented by Cmaj7, flat SI, RE, FA, The LA chord is represented as Bbmaj7. Minor seventh chord: Add a minor third to the minor triad, and use the uppercase English letter name of the root note plus "m7" to represent it. For example, LA, DO, MI, SOL chords are expressed as Am7, RE, FA, LA, and DO chords are expressed as Dm7. Minor major seventh chord: Based on the minor triad and a major third, use the capital English letter name of the root note. With the addition of mM7, chords such as DO, flat MI, SOL, and SI are expressed as CmM7, LA, DO, MI, and sharp SOL is expressed as AmM7. The piano itself is a harmonic instrument, and piano works are multi-part music works, so, Playing chords and chord accompaniment textures well is a material construction project for playing piano works. In basic piano learning, triads and dominant seventh chords are highly used. The basic finger technique for triad playing is good two-note playing.