Guitar Theorist is a professional level guitar chord, scale, interval, and note computation program, that adapts to string detunings and placement of a capo. Chords and scales may be computed from user defined families, or from a large selection of predefined families. User data is organized into documents, which may be edited, filed, and printed. An intuitive fretboard and music notation interface, allows intervals and notes to be found instantly, and simplifies data entry. Chords, scales, and intervals, may be played through a sound card or MIDI port. The program's chord analysis feature allows chord names to be derived from groups of notes. Charts mirror for left handed guitarists.