Crystal Ball icon

Crystal Ball

Kreuder
Music Practice Tool Multimedia
Version
0.3
Size
12.1 MB
Requires
Android API 26+
4 / 5 · 2,339 ratings 0 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 240 chords up by hand, without playing a note. Sixths, ninths, 6/9 and 13ths included. * 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 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

First release.

• Detect a chord by ear — press, strum, and it names the chord and draws how to fret it.
• Runner-up chords one tap away, and other voicings of the same chord up the neck.
• Capo-aware shapes, with the choice of naming the chord you hear or the shape you play.
• Song sheets — capture parts chord by chord, reorder and rename them, fix a chord by hand, and share the finished sheet.
• Chord dictionary, themes, keep-screen-on, and backup/restore for songs.

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.

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