Always In Key
The scale-locking engine snaps every note into the active scale, so a wrong note is simply not on the table.
Real-Time Key & Scale Detection • Play-In-Scale Instrument
PlayScaler
PlayScaler listens to any music, figures out its key and scale in real time, and lets you play along on any instrument without ever hitting a wrong note.
Part of the MIDI Xplorer package for macOS · see how it plays · ask a question
Real-TimeLive key & scale detection
26Scale families
300+Key / scale combinations
12Keys covered
INSIDE PLAYSCALER
The Whole App, at a Glance
Real-time key detection, a circle-of-fifths key wheel, confidence and BPM, a live spectrum, color-coded detected chords, instrument categories, and a scale-locked keyboard — all in one native macOS window.
- 01Confidence ringLive key & scale with a real-time certainty score.
- 02Circle-of-fifths wheelThe active scale mapped around the key wheel.
- 03Live spectrumThe incoming audio visualized as it plays.
- 04Detected chordsColor-coded chords recognized in real time.
- 05Instrument selectorPiano, guitar, synth, strings, and bass on tap.
- 06Scale-locked keyboardEvery key snapped into the detected scale.
CORE PLAY-IN-SCALE ENGINE
Never Play a Wrong Note
Every note you play is intelligently mapped to the detected — or chosen — scale, so beginners and pros always sound in key.
Any Input, One Engine
The on-screen piano, your computer keyboard, and a hardware MIDI keyboard all run through the same scale-locking engine.
Toggle On Demand
Keep scale-locking on for guaranteed-in-key playing, or switch it off any time to play completely freely.
REAL-TIME MUSIC ANALYSIS
The Key of Any Track,
Detected as It Plays
Key & Scale Detection
- Automatic key and scale detection from live audio
- 26 scale families across all 12 keys (300+ combinations)
- From major and minor to modes and exotic scales
Chords & Tempo
- Live chord detection recognizes the progression as it happens
- BPM (tempo) detection keeps you in time
- Confidence meter shows how sure the detector is
You Stay in Control
- Manual override to lock any key and scale yourself
- Stop, reset, and re-analyze on demand
- Searchable key & scale picker for quick selection
FLEXIBLE LISTENING SOURCES
Detect the Key of Anything
Point PlayScaler at a live instrument, your whole Mac, or a single app — whatever you want to jam along with.
Microphone / Line-In
Detect the key of a live instrument or the audio in the room.
System Audio
Detect the key of anything playing on your Mac, from any source.
Per-App Capture
Point it at a specific app — like a streaming or music player.
Interface & Device Select
Choose your audio interface and input device for a clean signal.
PLAY IT YOUR WAY
Turn Any Keyboard Into a Scale-Locked Instrument
On-Screen Piano
Click to play with live highlighting of active and in-scale notes right on the keys.
Computer Keyboard
Perform on the QWERTY home row with Z/X octave shifting and an on-screen range indicator.
Hardware MIDI Keyboard
Auto-detects MIDI keyboards plugged in at any time — just play.
Color-Coded Chord Keys
Detected chords are assigned colors and mapped to keys, so one press triggers a full chord.
BUILT-IN INSTRUMENTS & SOUND
A Whole Instrument, No DAW Required
The standalone app ships with its own sounds, so you can open it and start playing immediately.
Bundled Sound Library
A dedicated grand piano plus a full General MIDI sound set — no external plugins needed.
Instrument Categories
Piano, Guitar, Synth, Strings, and Bass right at your fingertips.
Play Immediately
No DAW, no setup — the standalone app includes its own instrument so you can jam on day one.
STUDIO EFFECTS & VISUAL FEEDBACK
Shape the Sound,
See the Music
Studio Effects & Output
- Reverb with mix, room size, and damping for instant depth
- Delay / echo with time, feedback, and mix
- Master volume fader right in the main window
- Output device selection for headphone or monitor preview
Visual Feedback & Control
- Circle-of-fifths key wheel of the active scale
- Live spectrum display of the incoming audio
- Detected-chord panel with color-matched chords
- Clean, branded, native macOS interface
PRICING
Part of the MIDI Xplorer package
PlayScaler lives in the MIDI Xplorer ecosystem for macOS. Download and try it first, then unlock everything with a single one-time license — no subscription, no recurring fees.
One-time license
$49
macOS · no subscription
FREQUENTLY ASKED
PlayScaler Questions
Do I need a DAW to use PlayScaler?
No. PlayScaler is a standalone macOS app with its own bundled grand piano and full General MIDI sound set, so you can open it and start playing immediately without a DAW or any external plugins.
Can PlayScaler detect the key of Spotify or other streaming audio?
Yes. PlayScaler can listen to your whole Mac's system audio or capture a single app, so it detects the key, scale, chords, and BPM of streaming services, YouTube, or any other source in real time.
How accurate is the key and scale detection?
PlayScaler analyzes audio in real time and shows a live confidence meter for its key and scale estimate. You can always override the result manually and lock any of 300+ key and scale combinations yourself.
How does play-in-scale mode stop wrong notes?
The scale-locking engine maps every note you play into the active scale — on the on-screen piano, your computer keyboard, or a hardware MIDI keyboard — so notes outside the key are snapped in and you stay in key the whole time.
Is PlayScaler part of MIDI Xplorer?
PlayScaler is part of the MIDI Xplorer ecosystem for macOS. Download and try MIDI Xplorer to get started, and see the pricing page for current one-time license details.
JAM IN KEY WITH ANY SONG
Sound like a pro on day one — no wrong notes.
PlayScaler turns any track into a scale-locked jam session: detect the key in real time, then play along on any instrument and stay in key the whole way through.
Jam in key with any song — instantly.
The key of any track, detected in real time.
Sound like a pro on day one — no wrong notes.
Turn your computer keyboard into a scale-locked instrument.