When I was first shown the modes, they were laid out for me in the key of C. It was a helpful start, but a limited one. I couldn’t see how the modes related to each other, and I had no way to view them side by side in every key. This app is the answer to that. It takes everything I built into The Music Theory Cheat Sheet and makes it move: pick any root, any scale, and every chord that lives in it appears at once, ready to hear and to play. Here’s how to find your way around.

Root row

Start here. Pick your tonic, and all seven columns rebuild on the spot. I let the app choose the cleanest spelling for you (B♭ over A♯, F♯ over G♭), so you’ll only ever see a double accidental when the scale genuinely calls for one.

Scale menu

Every mode of the major scale, plus the harmonic minor, melodic (jazz) minor, and altered scales. These are the same families the book is built around. The formula line under the key name spells out the steps as you go (W = whole, H = half).

Stack selector

This decides how tall each chord is built, from plain triads all the way up to the 13th, where the whole scale stacks into a single chord. Clean stacks get clean names (G13); the spicier tensions get spelled right out for you, like Em7(♭9,11,♭13).

Play scale

Plays the scale up one octave so you can hear its character before you ever build a chord on it. Everything you hear is tuned to A440.

Metronome

To the right of the Root/Key row is a lofi metronome with a warm kick and snare. Hit play and it lays down a steady backbeat to practice over. Use the −/+ buttons for one beat at a time or drag the slider to jump around the tempo, and the slider beside it sets the volume. It runs no matter what else you’re doing, so you can throw a beat on while you noodle through a scale or work out a chord.

The scale maps

Beside the key name you’ll find the whole scale laid out twice: once on a two-octave keyboard and once across fifteen frets of the guitar neck. Roots glow amber, every other scale tone sits in sage, and each note is marked with its degree. These aren’t just pictures: click any note on either map to hear it, at the true pitch of that key or that string and fret. It’s the fastest way I know to get a scale under your ear and under your fingers at the same time.

Mode Practice Mode

This is a tool I’ve always wanted, and couldn’t find. It turns the whole page into an ear-training tool. Tap ♬ Mode Practice Mode and three things happen: the keyboard and fretboard grow so they’re easier to read, the chord columns lose everything but the essentials (the note name, the chord spelling, and the charts), and a second button appears: Drone.

Hit the drone and the app holds a soft, sustained power chord, just the root and the 5th, on whatever key you’ve selected. A power chord is deliberately neither major nor minor, so it sits underneath every mode without fighting it. Now you improvise: play your own instrument, or click up and down the enlarged keyboard and fretboard, and listen to how each note of the selected mode sounds against that steady tonic and fifth. The ♭3 of Dorian, the ♯4 of Lydian, the ♭2 of Phrygian. This helps you stop reading about what makes a mode sound the way it does and start hearing it. Change the key and the drone follows; change the scale and the keyboard and fretboard maps light up the new notes and intervals to try over the same drone.

My advice: pick a mode, turn on the drone, and just wander the scale slowly until a few notes start to feel like home and others feel like tension. That feel is the whole point. It’s the thing the charts can show you but only your ear can teach you. Tap Mode Practice Mode again to return to the full view.

Play the Changes

This is the one I’m proudest of. Tap ♫ Play the Changes, pick a progression, and watch its chords move across a big keyboard and fretboard in real time, bar by bar, locked to the metronome. Drag the tempo and the changes speed up or slow down with it. You can let it run with Play, or step through a bar at a time with the arrows, or jump straight to any chord by clicking its column. It’s the closest thing I’ve found to having the chords come off the page and onto the neck while you’re actually playing.

The free edition runs the 1–4–5, the 1–5–6–4 and the 12-bar blues here, and the Triads / 7th selector up top drives it: flip to 7ths and the sevenths land right on the neck alongside the triads. The full app opens up the other five progressions and plays the blues with its dominant 7ths. The Keyboard / Fretboard switch lets you blow one up to full size depending on your instrument, and the fretboard runs all the way to the 20th fret here so you can see the whole neck. Underneath, only the chords actually in the progression stay on screen as full columns, so you keep the note pills, the Chord and Arpeggio buttons, and every diagram, but just for the chords you’re working. A marker rides above whichever chord is sounding, and the little dots track how far through the bars you are. Want to sit on a chord longer? Tap the + beside its dots to give it another bar, up to four, or the − to take one away, so a 1–4–5 can hang on the 5 for two bars before it comes home. The app remembers your bar counts for each progression. The 12-bar blues keeps its form.

The Fretboard Cage

The name’s a wink at the CAGED system, but you don’t need to know CAGED to use it. Under the neck are two handles. Drag them to box off any stretch of frets you want, and the fretboard hides every note outside that window, leaving only the chord tones inside it. A second pair of handles stands up the left side for the strings, so the box crops both ways: pull them together to study one string or a few next to each other, open them for all six. Between the two axes you can box off any little rectangle of the neck and hide everything else. Slide that box up and down the neck and you’ll see the same chord laid out in each position, which is the whole idea behind CAGED without the memorizing: every shape is just the chord tones that happen to fall under your hand in that spot. Open the handles all the way and you’re back to the full neck with every chord tone showing, which is its own kind of map. I built it because boxing yourself into one position and really learning what’s there is one of the fastest ways to get free on the neck.

The accompaniment

This turns the mode into a backing band. The Accompaniment switch gives you Off, Root, Root + 5th, or Triad, and whatever you pick follows the changes, re-voicing itself on the downbeat of every bar so there’s always a bed under you to play over. The root sits down low like a bass player and the rest fills in the middle, leaving the top open for you. Start with just the root if you want your ear to do the work, or fill it out to the triad when you want to hear the whole color. It’s the same soft tone as the drone, just moving with the chords instead of holding still. Stopping either the changes or the metronome stops everything together, so you’re never left with a beat running under silence.

Intervals or notes, and the whole board

On the big fretboard you can flip the dots between Intervals and Notes. Intervals keep your eye on the shape (root, 3rd, 5th, 7th); notes show you exactly which pitches you’re on, spelled right for the key you’re in. The keyboard already names everything, but the guitar isn’t laid out in a straight line, so being able to switch is a real help. And there’s a ♮ Full board button that pops up the entire neck with every note labeled, roots in amber, the way I always wished I could glance at when I was starting out. Click any note on it to hear it.

Common chord progressions

This is the second half of the book, brought to life. The menu holds the progressions I leaned on most: 1–4–5, 1–5–6–4, 1–6–4–5, 1–5–6–3–4, the 2–5–1, the 3–6–2–5–1, the 7–3–6, and a full 12-bar blues with the quick four and turnaround. Choose one and the columns line up in the progression’s own order, bar by bar, every chord still carrying its charts. Then hit Play to walk through it. Longer forms like the blues trim down to bar number, chord name, and charts so the whole thing fits in front of you; click any chord name to hear it. When you’re done, pick “← Back to scale view” at the top of the menu, or the button beside it. And here’s where it goes past the printed page: switch to harmonic minor and the minor 2–5–1 builds its iiø7 and V7 on its own; raise the stack and the same progression turns into the jazz voicings from the back of the book.

Each chord column

Click the note at the top of a column to hear that scale tone by itself. The small number beside it is the Nashville degree, the scale step with its accidental against the parallel major, so Dorian reads 1 2 ♭3 4 5 6 ♭7, the way you’d call it on a gig. Below the chord name you’ll find its mode and its classical function (Mixolydian · Dominant), exactly as they sit in the book’s charts.

Reading the chord symbols

An uppercase numeral is a major-third chord, lowercase is minor, ° is diminished, ø is half-diminished, and + is augmented. The color tells you the same thing at a glance: amber for major, sage for minor, rust for diminished, violet for augmented.

The note pills

Each pill is one note of the chord, marked with the job it does (R, 3, ♭7, ♯11…). Click one to hear just that note at the pitch it actually sits in the voicing. Click down the stack in order and you’ve played the arpeggio with your own hand.

Chord & arpeggio

Chord sounds all the notes together. Arpeggio rolls them up one at a time and lands on the octave root.

Piano & guitar charts

Every key and every dot is labeled with the interval it’s playing, so you always know what your fingers are on. Each chord comes with a piano chart and two guitar shapes: the open / basic grip sits low and uses open strings where it can, while the barre / movable grip is fully closed. Learn it once and slide it to any key. On guitar, × means don’t play that string, ○ means play it open, and a number to the side tells you which fret you’re starting from. From 9th chords up, the grips become shell voicings: root, 3rd, 7th, and the color tone, with the 5th and doubled roots set aside, the way working players actually voice them. Click any chart to open it up large, and in there, every note is playable: click a highlighted key or any dot on the guitar grips to hear that exact pitch. On triads and 7th chords you’ll also get inversion buttons (root, 1st, 2nd, and 3rd for sevenths) that re-voice both the piano and the guitar with that note in the bass, and the notes stay clickable through every inversion, so you can hear the voicing change as the bass moves.

Play it on a MIDI keyboard

MIDI mode is part of the full app. Tap the MIDI button to try it free for 14 days.

Plug a MIDI keyboard into your computer, tap 🎹 MIDI, and the app turns into an instrument. After you allow it once, MIDI turns itself on whenever your keyboard is plugged in. Pick Rhodes or Wurlitzer for the sound. Vibrato works the way each instrument did it: the Rhodes Suitcase swirls between the left and right speakers, the Wurlitzer pulses the volume. Verb sets how much reverb is around the sound. The rest of the app plays the Wurlitzer too: every note you tap, the chord and scale buttons, and the Play the Changes backing. The mode drone stays a synth pad, and the Vibrato and Verb settings for the Wurlitzer carry over to the whole app. If you’d rather not name anything against a key, flip the panel from In key to Chromatic: chords get their plain names, with no Roman numerals, and the maps show only the notes you play. Everything you play comes through the app’s own tone, and the panel names what’s under your hands in the key you have selected. One note shows its scale degree. Two notes show the interval, named from the lower note, so C up to B reads as a major 7th, 7 over 1. Play three or more and you get the chord name, its spelling, and its Roman numeral in your key. If the lowest note isn’t the root, it shows as a slash chord, like Am7/C.

When a chord comes from outside the key, the app tells you what it’s doing there, and right under it, where it wants to go next. An A major in the key of G reads II (V/V), the five of five, because it pulls toward D. A B♭ in C reads ♭VII, borrowed from the minor. A G minor in C reads v (borrowed from minor · ii/IV): it’s the two of four, so it leads to C7 and then F. It knows the tritone sub too (a D♭7 in C slides down a half step onto C) and the Neapolitan (a plain D♭ major in C sets up G7). When a chord fits two ways, you get both, the more common reading first. Color tones don’t throw it off: a G7 with a ♭9 in C is still the V7. Your notes light up on a keyboard and all across the fretboard too, so a chord you play on the keys shows up laid out on the guitar neck.

The sustain pedal works the way you’d expect: whatever is ringing counts toward the readout until you lift your foot. If your pedal works backwards and holds notes when it’s up, hit Reverse pedal. MIDI works in Chrome and Edge and in the desktop app. Safari and iPhone and iPad browsers don’t support it yet. Use wired headphones or speakers, because Bluetooth adds a delay you’ll feel.

Shortcuts

1–7 play the chords by degree · Shift with a number plays its arpeggio · S plays the scale · Esc closes any panel.

One thing you won’t find here

There’s no sheet music anywhere in this tool, and that’s on purpose. This is built for players who want to learn through theory, intervals, and their own ear, not through reading notation. Nothing against reading music, it’s a real skill and worth having. But that’s not what this is for. Everything here is aimed at helping you internalize the intervals, hear how the harmony is put together, and map the chord shapes onto your own instrument until they’re yours. The goal is to get this stuff off the page and into your hands and ears.

My hope for this is the same as it was for the book: that it becomes a tool you actually reach for, whether you’re just meeting the modes or already weaving them into your own writing and playing.