Casvelis

Casvelis turns music 🎵 theory into a living, cosmic instrument. Explore the circle of fifths, build 🔨 chords, study 📖 scales and modes, and design chord progressions — all rendered as a glowing constellation of key nodes, a central crystal, and luminous progression paths. Everything works completely offline 📴, with no ads and no accounts.

Whether you are a beginner 🌱 learning your first chords, a songwriter searching for the next progression, or a student revising for theory exams, Casvelis gives you a clear, beautiful, hands-on way to see 👀 how music 🎵 fits together.

WHAT YOU CAN DO

• Circle of Fifths — Tap 👆 through all 12 keys on an interactive glowing ring. See 👀 major keys on the outer ring, relative minors on the inner ring, and the IV/V neighbor and relative links light up as you explore.

• Key Detail — View each key's signature on a drawn staff, its diatonic chords (I through vii°), relative and parallel keys, and the scales available in it.

• Chord Builder — Pick any root and quality (major, minor, 7th, m7b5, dim7, sus, 9th and more). See 👀 the notes 📝 as chips, highlighted on a keyboard ⌨️, with intervals and scale degrees.

• Chord Detail — See 👀 a chord on both keyboard ⌨️ and guitar fretboard, cycle through inversions, view related chords, and read the exact frequency of every note 📝 (A4 tuning is adjustable).

• Scale & Mode Explorer — Choose a root and a mode (Ionian to Locrian, plus harmonic/melodic minor, pentatonics and blues). See 👀 notes 📝 and degrees on the keyboard ⌨️, the tone/semitone formula, a short "character" description, and the diatonic chords of the scale.

• Progressions — Start 🚀 from classic presets (I–V–vi–IV, ii–V–I, 12-bar blues and more) drawn as a glowing node-path with roman numerals. Transpose to any key, edit the steps, name and save 💾 your own progressions.

• Library 📚 & History ⏳ — Save 💾 chords, scales, progressions and keys, and revisit everything you have explored recently.

• Reference — A built-in glossary: interval table 📋, chord-formula table, mode-character table, and the order of accidentals.

• Share 🤝 Card — Create a shareable card of a chord, scale or progression over a procedural nebula background, or a photo 📸 from your camera 📷 or gallery 🖼️, and save the image to your device.

WHY CASVELIS ❓

• 100% offline 📴 — no internet connection needed, ever.
• No ads, no tracking, no accounts, no sign-up.
• No data collected or shared. Everything you save 💾 stays on your device 📱.
• Adjustable concert pitch (A4 Hz), sharp/flat notation, and a reduce-motion option for comfort and accessibility.

Casvelis is built for curiosity. Open the circle, follow the light, and hear how the theory connects.