Number from the thinnest string
String 1 is the thinnest and highest-pitched open string. String 6 is the thickest and lowest-pitched. In standard tuning, from string 6 to string 1, the notes are E A D G B E: mi la ré sol si mi. The two E strings share a letter name but sound two octaves apart.
On the app’s fretboard, string 1 is at the top and string 6 at the bottom. Fret 0 means an open string: pluck it without pressing a fret. These labels describe the diagram; they do not depend on how you hold your phone.
Move one semitone per fret
Each fret raises a string by one semitone. On string 6, the first four positions are E, F, F♯, G. On string 5 they are A, A♯, B, C. On string 4: D, D♯, E, F. On string 3: G, G♯, A, A♯. On string 2: B, C, C♯, D. String 1 has the same letter names as string 6, two octaves higher.
Natural-note mode leaves out the sharp and flat notes. An empty place in that mode is still a playable fret; it is simply outside the exercise’s selected note set. Start with one or two strings, then add another when you can name and locate their notes comfortably.
Try it yourself
What is string 2, fret 1?
Show the answer
C (do). The open second string is B; B to C is one semitone, so you move one fret.