This paper introduces a novel type of interactive visual aid—the chord circle—designed to support the teaching of triad and seventh chord construction within a given key. In contrast to the well-known circle of fifths and fourths, which primarily illustrates relationships between keys, our chord circle serves as a tool for building chords within a key. It enables users to visualize chords built from each degree of a selected tonality, including their component tones.

Our teaching approach focuses on the six-string guitar in standard tuning (E–A–D–G–B–E), and chords are presented using standard fretboard diagrams, providing students with both a visual and kinesthetic representation of chord shapes. A key contribution of this work is the development of a process model for chord construction using BPMN (Business Process Model and Notation), which formalizes the algorithmic logic behind generating playable chord shapes from input notes.

To make this method accessible and practical, we developed the web application aakordy.cz, which offers an interactive chord circle, real-time fretboard visualization, and validation of chord composition. The article also presents statistical evaluation data gathered from students who used the tool during guitar instruction. Our findings show that the integration of visual and process-based models significantly enhances the understanding of tonal relationships and chord structure, contributing to more effective learning in both music theory and instrumental practice.

Keywords: Chord construction, BPMN in music education, guitar pedagogy, fretboard visualization, music theory tools, interactive learning application.