Canon in D is mainly composed of two composing techniques: the "Canon" created by 3 violins, and the "Basso Ostinato" created by the bass instrument(s). The title "Canon in D" mainly refers to the "Canon" which created by the violins.
Pachelbel's Canon. Credit: Wikimedia Commons
Canon means different voices play the same melody but starting at different time-spots, resulting an overlapped and intertwined effect. It's a typical example of polyphonic music, meaning that the notes in each voice can be regarded as melody and harmony, creating a unique musical texture.
Basso Ostinato is a repeating bass-melodic-line in a piece of music. It is often used as an introduction, and is repeated throughout the piece until the end. The basso ostinato of Canon in D is made up of 8 notes (D-A-B-F#-G-D-G-A). It is known as the Romanesca Sequence, which was popular in the 16th and 17th centuries, often used in church music.
Classic FM. (24 May, 2019). How did Pachelbel’s Canon in D become the most popular wedding song?. Retrieved 26 January, 2023 from https://www.classicfm.com/composers/pachelbel/music/pachelbels-canon-d-facts/
Galaxy Music Notes. [n.d.]. Learn About “Canon and Gigue in D” by the Baroque Composer Johann Pachelbel. Retrieved 26 January, 2023 from https://galaxymusicnotes.com/pages/learn-about-canon-and-gigue-in-d-by-the-baroque-composer-johann-pachelbel
Johann Pachelbel, Public domain, via Wikimedia Commons. Retrieved 26 January, 2023 from https://commons.wikimedia.org/wiki/File:Pachelbel%27s_Canon_-_Mus.MS_16481-8_Page_1.jpg.
Levine, Alexandra S. (9 May, 2019). “How ‘Canon in D Major’ Became the Wedding Song”. Retrieved 26 January, 2023 from https://www.nytimes.com/2019/05/09/fashion/weddings/canon-in-d-major-wedding-song.html
Schwarm, B. (16 May, 2020). Pachelbel’s Canon. Encyclopedia Britannica. Retrieved 26 January, 2023 from https://www.britannica.com/topic/Pachelbels-Canon