The Idea
Any instrument with strings is really the same instrument: a grid of intervals laid across a neck. You choose how the strings are tuned — a violin climbs in fifths, a guitar mostly in fourths, an oud or a bağlama in a tuning of its own — and the distances between them decide where every pitch lands. String Logic starts from those distances rather than from letter names. The root becomes 1, and everything else is a distance from it. Set your tuning and the neck answers; retune and it redraws. Nothing about the app is baked to one instrument.
It speaks the twelve tones nearly every tuning tradition shares — the common floor beneath the frets and the finger positions alike. So a player whose tradition adds notes between those twelve can still use String Logic to reach into Western harmonic logic — triads, scales, voice leading — on their own strings, in their own tuning, simply leaving the microtones aside for a moment. A bridge, walked in either direction.
The founder's own way in was the guitar. Read it in standard tuning — E, A, D, G, B, E — and four of those steps are a perfect fourth while one, G to B, is a major third: a single seam every guitarist learns to step over so early they forget it is there. Move that one string up a semitone and the seam closes into all fourths, E, A, D, G, C, F, and a shape becomes the same shape everywhere. That seam is an inheritance, not a law — the argument of a 2006 master's thesis, now something you can check for yourself in ten seconds. It is one instance of the larger idea, not the boundary of it.
How It Works
Build a Pitch Set on the Grid
In EXPLORE, choose a root and switch intervals on and off around the wheel — root, third, fifth, flat seven, whatever the idea needs. You are working in intervals, not fingerings. The set is the thought.
Let the Neck Answer
The neck fills in underneath — every place that pitch set lives on the strings, in whatever tuning you have set, fretted or bowed. Change the tuning and the diagram re-draws itself; the intervals stay put while the shapes rearrange.
Hold It Up to the Tuning Lens
Put two tunings side by side — a guitar's fourths against its standard, say — with the same idea on both. Tap it and hear how the same intervals fall differently under two tunings, back to back. Twenty years of prose collapses into a single scroll.
Hear It, Then Hand It On
Play the set, walk it through modes and voicings, drill it by ear. When it is worth keeping, capture it — as a lesson link that carries the entire setup in a URL, or as a clean, branded A4 lesson sheet.
Key Features
Interval-Grid Pitch-Set Builder
Build any pitch set by switching intervals on and off around the wheel. You think in function — root, third, fifth, seventh — and the app keeps the notes.
Any Tuning You Like
Guitar in fourths or standard, bass, ukulele, the violin family in fifths, mandolin, banjo, oud, bağlama, or a tuning of your own. Set the strings however you play — any count, any interval — and everything follows.
The Tuning Lens
Two tunings at once — a guitar's fourths and its standard, for instance — the same idea placed on both, so you can hear and see how a tuning reshapes where the intervals fall.
The Neck for Any Tuning
Every place a pitch set lives on the strings, drawn for the exact tuning you set — fretted or a bowed fingerboard alike. Retune and the diagram redraws itself, intervals intact.
Modes, Subsets & Supersets
Turn a set through its modes, or step out to the scale it belongs to and in to the smaller sets hiding inside it. One idea, seen from every side.
The Pattern & Rhythm Dial
Give a pitch set a shape in time — a rotating dial sets the order and the pulse, so a set becomes a phrase you can actually play along to.
Harmony Lane & Voice Leading
Lay chords along a lane and watch the voices move between them — the intervals doing the leading, one note at a time.
Ear Drill
Train the sound of each interval and set against your ear, so the shapes on the neck end up connected to what you actually hear.
Reflect & Smoothest Tour
Invert a set with a single reflection on the wheel, or let AUTO walk it up the neck by the smoothest path from position to position.
Lesson Links
Share the whole setup — root, set, tuning, diagram — as a single link. Open it and you land exactly where the sender was.
Branded A4 Lesson PDFs
Export a clean, printable lesson sheet of any set or collection — black-and-white for the printer, dark for the screen.
The 2048 Pitch-Set Universe
Every pitch set there is to have, browsable and drillable — the full library behind the wheel, there when you want to wander.
Play-Along with THE BAND
Import an iReal chart with its MIDI and play over it, the lane and diagrams following the changes as the band moves through the tune.
Dark Interface
Built for dark mode from the ground up — easy on the eyes in a practice room or a studio with the lights down.
Who It's For
Guitarists & Bassists
Whether you play standard, all-fourths, drop tunings, or five and six strings, the neck is drawn for your tuning — and the intervals stay the same across all of them.
Bowed Players
Violin, viola, cello, double bass — the fingerboard tuned in fifths, the same interval logic drawn where your fingers actually land.
Mandolin, Banjo & Folk Strings
Fifths, reentrant tunings, ukulele, charango, balalaika — set the strings your instrument uses and the diagrams follow.
Oud, Bağlama & World Strings
Fretless or fretted, tuned your way. Use the twelve shared tones to reach into triads, scales, and voice leading on your own instrument.
Teachers
Build an idea once, hand it over as a lesson link or a printed sheet, and let the student open it exactly where you left it — on whatever they play.
Composers, Arrangers & the Curious
Sketch with pitch sets, turn them through modes and voicings, hear the voice leading — or simply wander, and hear what a tuning does to an idea.
Free, with One Optional Upgrade
String Logic is free to download, and the free tier is meant to be genuinely useful on its own — build pitch sets, hold them up to the Tuning lens, and hear them. When you want the deeper toolkit, one optional Pro upgrade unlocks it. One purchase, no subscription. No ads, no gamification.
Free
- Build pitch sets on the interval grid
- The Tuning lens — fourths and standard, side by side
- Play any set and hear it
- The neck for your tuning
- Enough to genuinely use the app, not just preview it
Pro Unlock
- The deeper set of tools for daily study
- Modes, subsets, supersets & the 2048 universe
- Harmony lane, voice leading & ear drill
- Lesson links & branded A4 lesson PDFs
- Play-along with THE BAND
- Restore on any Apple device with your Apple ID
Introductory price. Pro opens at $4.99 for the first two weeks after launch, then settles at $7.99. One purchase, yours to keep — no subscription, ever.
Built by One Developer
String Logic is built by Çağlayan Yıldız at Puja Music Productions in Antalya, Turkey. It began as a master's thesis in 2006 — Standard Guitar Tuning: A Historical Mistake? — and grew, over about thirty years of playing in all-fourths, into the app he wished he'd had in the room when he defended it. It sits alongside AllGoRhythmics, MathRonome, and Elvin's Numbers — pieces of one music education system.
One developer. No ads, no tracking, no data collection. Your work stays on your device.
Frequently Asked Questions
No. Set any tuning you like — a guitar's standard or all-fourths, a violin's fifths, a bağlama, or one of your own. The Tuning lens simply lets you see and hear two tunings side by side when you want to. Nothing asks you to change how you actually play.
Yes. String Logic isn't a guitar app that happens to allow other tunings — it works from the intervals up, so it fits any stringed instrument. Set your strings — however many, at whatever intervals — and the neck is drawn for exactly that. Bass, violin, viola, cello, mandolin, banjo, oud, bağlama, ukulele: they're all just different tunings of the same idea.
It works in the twelve tones nearly every tuning tradition shares — the common ground beneath most music. If your tradition adds microtones between those twelve, String Logic won't voice them, but you can still use it to explore triads, scales, and voice leading on your own instrument, in your own tuning, setting the in-between notes aside for a moment. Think of it as a way into shared harmonic logic, not a replacement for the sounds your tradition adds.
A lesson link is a single URL that carries the whole setup — the root, the pitch set, the tuning, the diagram. Send it to a student or a friend, they tap it, and String Logic opens exactly where you were. It's the fastest way to hand someone an idea without rebuilding it by hand.
It's for anyone who wants to understand the neck through intervals rather than memorized shapes — which is a gentler starting point than it sounds. A beginner can build a set and watch where it lives on the strings; a working player can drill modes, voice leading, and the 2048-set library. It meets you where you are and goes as deep as you want.
Yes. Every set and diagram can be played back, so you hear what you're looking at — including the Tuning lens, where the point is to hear the difference between the two necks. The ear drill trains that connection between the shape on the neck and the sound in your ear.
String Logic is built for iPhone and iPad. It isn't on the App Store yet — leave your email and we'll tell you the day it lands.
Soon. It's finished and in final testing. Write to info@pujamusic.com and we'll let you know at launch.