Guitar Theory Studio turns your phone into an interactive fretboard, chord book, and practice partner. Explore any scale, key, or CAGED shape on the Fretboard Explorer. Build and hear chord progressions with the Chord & Progression Builder — free for every user. The progression builder comes with a library of 20 classic progressions — the ones behind songs like Don't Stop Believin', Stand By Me and Sweet Home Alabama — in any key. Every chord is numbered in both Nashville Number System notation and Roman numerals, so you can read a progression as theory and move it to another key instantly. All free, no account needed. Unlock Premium to add Arpeggios — diatonic sweep patterns for every chord in a key, generated from the progression you actually built — and Practice Loop, a metronome-driven drill generator. Practice major, minor, harmonic minor and melodic minor as three-notes-per-string patterns across all seven positions, plus pentatonic and blues boxes, with ascend, descend and bounce sequences and unlimited saved presets. Notes and chords are spelled the way the key is actually written — B flat in F major, not A sharp — so what you read here matches what you read anywhere else. Whether you're learning your first scale or building a practice routine that actually sticks, Guitar Theory Studio keeps theory and the fretboard in the same place. Terms of Use (EULA): https://guitartheorystudio.com/terms.html