ChordProgressions.org vs OtoTheory

ChordProgressions.org is a free browser studio for creating, hearing, analyzing, customizing, and exporting chord progressions for guitar and piano. Its tools include generators, builders, finders, identifiers, analyzers, and transposers. Guitar shapes and piano voicings can be adjusted for tuning, capo position, difficulty, inversions, and fingering. Theory views show Roman numerals, Nashville numbers, chord functions, cadence points, borrowed chords, and an estimated key with confidence. The studio accepts MIDI input and imports MusicXML, project files, and plain-text chord sheets. Browser audio analysis creates an editable chord timeline with a confidence score. Exports include MIDI, WAV, chord-chart PDF, PNG and SVG diagrams, plain text, CSV, JSON, MusicXML, and share links. Projects autosave on the device, and imported files are read locally. Practice tools loop progressions with metronome and count-in, plus ear and playing exercises in every key.

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.