Crystal Ball icon

Crystal Ball

Kreuder
Music Practice Tool Multimedia
Version
0.6
Size
13.2 MB
Requires
Android API 26+
4 / 5 · 2,339 ratings 11 downloads

Updated Sep 22, 2026

Quick answer

Detects guitar chords and combines them into song sheets.

F-Droid repository metadata

Crystal Ball listens to your guitar and tells you what chord you just played. Press Detect single chord, strum, and it names the chord and draws how to fret it — with the chords it nearly picked instead one tap away, and other ways to play the same one further up the neck. Capture a whole part and it becomes a song sheet you can keep, correct and share.

Early-stage release — expect rough edges. Feedback and bug reports welcome via Issues.

Features:

* Detect a chord by ear — press, strum, done. It listens until the answer settles rather than for a fixed time, so a clean open chord resolves in about a third of a second; strumming again restarts it, so a bad take needs no second press. * Ranked alternatives — the best fit is a guess, not ground truth, so the runner-ups sit under it and one tap swaps the page over to any of them. * Chord shapes, not just names — the most idiomatic grip drawn large, plus other voicings walking up the neck. Open shapes are the ones a player expects to see, by name. * Capo-aware — detection is unaffected (the microphone hears the real chord either way), but the shapes are redrawn behind the capo, fret numbers stay as printed on your neck, and anything the capo pushes off the end is dropped rather than offered. Chords can be named by what you hear or by the shape your hands make. * Song sheets — capture a part chord by chord, name it Intro or Chorus, reorder the parts, and read the whole song back as diagrams. Parts can be renamed, chords fixed by hand without playing them again, and the finished sheet shared to any app. * Chord dictionary — look any of 252 chords up by hand, without playing a note. Power chords, sixths, ninths, 6/9 and 13ths included. * Chord finder — set the dots on a guitar neck and it names the shape, slash bass included, with other names for the same notes and chords a finger away. Behind a capo it names what sounds, and the capo drags along the neck. * English and German — pick the app's language without changing the whole phone. German note names (H/B) are a separate switch, since being taught H is not the same as reading German. * Session comforts — System/Light/Dark themes, keep-screen-on, an optional capo prompt at launch, an in-app quick help sheet, and backup/restore for your songs. Preferences persist across launches.

Heard: maj, min, 7, maj7, m7, sus2, sus4, across all 12 roots. Drawn: those plus 5, dim, aug, m7b5, dim7, 7sus4, 6, m6, add9, 9, maj9, m9, 6/9 and 13 — yours to look up and write down, though the microphone will not name them. Shapes assume standard tuning (EADGBE).

Honest about accuracy: template matching on clean triads is good, and degrades on a boomy room, a badly tuned guitar, or a phone held across the room. It is a practice aid, not ground truth — hence the runner-up row, which is one tap from correcting it.

Microphone access is required — listening to your guitar is the whole app. Audio is analysed on the fly and never recorded, stored or sent anywhere; the app has no network permission at all.

No ads, no trackers, no network access.

Screenshots

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What’s new

Set the dots, read the name: the new Chord Finder is the dictionary backwards.

• Tap a grip onto a guitar neck, or type one like x32010, and it names the chord, slash bass included.
• "Did you mean" offers other names for the same notes, and chords a finger away.
• Behind a capo it names what sounds. Hold the capo on the neck to drag it.
• Power chords join the library, making 252.
• Chord Finder has its own button on the home screen.

How to install

  1. Download the APK from the button at the top of this page.
  2. Allow “Install unknown apps” for your browser or file manager only, not for every app.
  3. Open the downloaded file and confirm the installation.
  4. If installation fails with “App not installed,” remove an earlier build of the same app first. A signature conflict is the usual cause.

Data safety

  • Every file is checked against its published SHA-256 before it is listed.
  • Files are scanned for malware on every update.
  • The permissions each app requests are listed on its own page.
  • Read the full safety policy for how we test, flag, and delist files.

Frequently asked questions

What is Crystal Ball?
Detects guitar chords and combines them into song sheets.
Who develops Crystal Ball?
Crystal Ball is developed by Kreuder.
Which Android version does Crystal Ball require?
Crystal Ball requires Android API 26 or later.
What is the current version of Crystal Ball?
The synchronized F-Droid version is 0.5.
Which license does Crystal Ball use?
The signed F-Droid metadata lists GPL-3.0-only.
Where is the source code for Crystal Ball?
https://github.com/mkay/CrystalBall

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