ChordSequence vs OtoTheory

ChordSequence is a free set of browser-based music tools for composing and exploring chord progressions. Its player performs chords selected by the user with drums, bass, piano, guitar, and synth, drawing on 548 rhythms that include pop, rock, salsa, and reggae. You can reorder chords, arrange them into sections, loop those sections, and edit individual instrument parts. The mixer offers volume, pan, mute, solo, EQ, and compression controls for each instrument, plus reverb for the overall mix. Songs can be exported as WAV audio or MIDI notes for use in a DAW. Other tools include a chord finder, transposer, key detector, Circle of Fifths, tuner, metronome, guitar and bass tabs, and a drum machine. The browser player is stated to work in Chrome, Firefox, Safari, and Edge. An Android app works offline, needs no account, and supports Android 8.0 or later; iPhone users can use the browser player. The Free plan is free, with all features, no usage limit, and WAV and MIDI export.

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.