Open—Shape vs OtoTheory

Open—Shape helps guitarists find playable chord voicings across the fretboard, including in different tunings. Its chord engine searches for shapes, filters them by note count, and supplies difficulty labels and fingering details. Users can chain and reorder chords, play progressions, and save them. The Free plan includes the full chord engine, every voicing, 33 built-in tunings, real acoustic guitar playback, a microphone tuner, and up to three saved progressions. Pro costs $9.99, paid once, billed one-time, and adds unlimited custom tunings and saved progressions. The tuner identifies strings in alternate and custom tunings; capo settings update chord voicings and progressions. A visual Canvas board for connecting chords, tuning, and capo runs in a desktop browser. Open—Shape is available on iOS and the web, and an account is not required. Saved tunings and progressions are stored in browser local storage, with backup export and import in Settings. Its privacy policy says tuner audio is analyzed in the browser and is not recorded or transmitted.

OtoTheory is a chord progression builder and music theory companion for guitar, bass, and keyboard players, songwriters, and DAW users. Its iOS app can identify chords, key, and song sections from imported audio or an on-device guitar or piano recording. Users can paste progressions from ChatGPT, Claude, or Gemini for Roman numeral analysis and playback with grooves. The app lists 19 groove patterns and more than 50 progression presets; OtoTheory AI suggests chords using musical feel, theory, and emotion. Pro exports MIDI in Groove, Groove + Theory, or Chords Only modes, including BPM, section markers, and chord names. The maker says those exports can be used with Logic Pro, Cubase, Ableton, and other DAWs. OtoTheory is available on iOS and the web, but the web version has fewer features and Pro is iOS-only. The free iOS plan allows three local sketch saves and excludes MIDI and audio export. Pro is listed from $5.99/mo; its annual plan is $49.99/year, and Lifetime costs $99.99 once.