Fretboard

Fretboard is a guitar theory app that lets users see where the notes corresponding to a given chord, or to a complete scale, occur along the length of a guitar's fretboard. For chords, users can specify the root note, type of chord, and guitar tuning. Similarly, for scales. The fretboard is drawn using the D3.js library.

A live version is here

Internally, the program represents notes as integers (0 for C, 1 for C#, 2 for D etc.). Thus enharmonic equivalents, like C# and Db, are represented by the same integer. One problem is to then recover the correct name for a note in the context of a given key (e.g. in the Bmaj scale, it's called "C#", but in the Fmin scale it's called "Db"). I'm not certain that the program solves this problem correctly in all cases (especially for chords). If you come across bugs, please email at: mrieppel at gmail dot com.