Reading the notes and intervals
Choose a root note, then a scale or chord type. For C major, the scale is C–D–E–F–G–A–B; its semitone intervals from C are 0, 2, 4, 5, 7, 9 and 11. A C major triad uses C–E–G, at intervals 0, 4 and 7.
Use Play Scale for an ascending note sequence, Play Chord to hear notes together, or Play Arpeggio to hear them separately. Compare the notes with your instrument or a melody you are writing.
Audio uses synthesized tones in equal temperament, with A4 at 440 Hz. This is a note reference, not a microphone-based chord detector. Enharmonic spellings can differ from those used in a particular score.