If you’ve ever searched for how to learn piano chords or wondered what maj7, m9 or sus4 actually mean, you’ve probably ended up with static charts and YouTube videos that move too fast. Music theory is actually simple — once you can see it and hear it at the same time. That’s why we built SR Keys: a free interactive music theory tool that runs in your browser, with no installation and no sign-up.

An interactive keyboard with 4 synthesizer sounds

The foundation is a three-octave keyboard where every chord and scale appears visually — the root note in green, chord tones in blue, with interval labels on every key (R, ♭3, 5, ♭7). The sounds aren’t generic samples but four carefully synthesized instruments:

• Grand Piano — tuned via spectral analysis of a real Soft Grand recording: soft attack, dark spectrum, long singing sustain
• Moog Pad — a warm analog-style pad with a slow filter sweep
• Juno — DCO saw + sub oscillator through a Roland-style BBD chorus: short stereo delay lines with inverted LFO polarity create that instantly-wide shimmer classic Juno synths are famous for
• Detroit Strings — a Solina-style poly-string ensemble: four detuned oscillators, an octave layer, slow swell and a floating ensemble chorus — the sound of Detroit techno string chords

Every chord and scale — explained, not just displayed

The library covers 23 chord types: triads (major, minor, dim, aug, sus2, sus4), sevenths (7, maj7, m7, dim7, m7♭5), and extended/altered harmony — 9, maj9, m9, 11, 13, 7♭9 and the “Hendrix chord” 7♯9. Plus 14 scales and modes: major, three minors, pentatonics, blues, Dorian, Phrygian, Lydian, Mixolydian, Locrian and whole tone. Each comes with its notes, formula and a short note on where it’s used — for instance, why m9 chords are the backbone of deep house harmony.

Harmony palette & progressions: which chords belong together

Instead of learning chords in isolation, the “Chords That Work Together” palette shows the full chord family of any key: triads with Roman numerals, diatonic sevenths and sus chords — with empty slots where a chord simply doesn’t exist in that key. Eight classic chord progressions play at the press of a button: POP (I–V–vi–IV), JAZZ (ii–V–I), SOUL, EPIC, ANDALUSIAN — while you watch the chords change on the keyboard.

Transition matrix & interactive circle of fifths

Two visualizations you’ll rarely find interactive and free: a 7×7 functional-harmony matrix (which chord leads where — click any cell to hear both chords back to back), and an interactive circle of fifths — the map of all keys with their relative minors, where clicking any segment moves the whole tool into that key.

Inversions: why pianists’ progressions flow

Every chord can be played in root position or 1st, 2nd and 3rd inversion — the same notes in a different order. That’s voice leading: the secret of why C→F→G flows for experienced players and jumps for beginners. With the INV buttons, you see and hear the difference in ten seconds.

Recorder, loop and MIDI export — from idea to DAW

Found a progression you love? REC captures 4–8 chords, LOOP plays them at an adjustable tempo, and EXPORT MIDI downloads a standard MIDI file for Ableton Live, FL Studio or Logic Pro. There’s also Drag to Desktop: grab the MIDI chip and drag it straight onto your Desktop (Chrome/Edge), then into your DAW — the fastest route from sketch to production.

🎧 Ear training quiz: test your ears

Looking doesn’t build an ear — guessing does. Quiz mode is genuine free ear training online across 5 levels: Major vs Minor, Triads, Sevenths, Extended chords and Intervals. The tool plays a hidden chord, you name it, and the answer is revealed visually on the keyboard. Score and streak counters included.

🔍 Identify + MIDI keyboard: you play — it names the chord

The reverse mode: click keys and the tool recognizes them — intervals (“perfect 5th”) and chords with inversion detection (“C · 1st inversion — E in bass”). Connect a MIDI keyboard via Web MIDI and it names your chords live as you play — perfect for working out the chords of songs you love.

Conclusion

SR Keys brings chords, scales, progressions, the circle of fifths, ear training and a MIDI workflow into one place — everything you need to learn music theory online, visually and for free. Open it in your browser and start with your first chord.

*SR Keys is part of the free music tools series on AICreativa.mk: [SR-303 Acid Bassline Synthesizer] and [SR Rhythm Sequencer]