Gridtone builds a Quad Cortex chain from a player, a song and the part you want to play, and checks every setting against the unit before you see it. Founded and designed alone, and built with Claude Code in twelve days. It's in beta at gridtone.app, open for testing.
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I play guitar, and I love my Quad Cortex. It can get close to almost any rig I have wanted to play through. Getting it there is another matter. Its library of amps, cabs and effects is huge, and the names don't always tell you what you are looking at: Gilmour's Hiwatt is Watt D103 Bright, the Big Muff is Fuzz Pi. Finding the tone of a player I love meant guesswork and a lot of trial and error.
Gridtone is what I built instead. Name a player, a song and the part, and a chain lands on a grid laid out like the Quad Cortex's own. Before you see it, every block and setting is checked against a catalog of 265 Quad Cortex models and 7 cab mics, and every fix is listed.
I founded it, designed it and built it alone: from a mockup on 3 October 2026 to a public beta with accounts, a free tier I pay for and a full design system, twelve days and 202 commits later. Claude Code wrote most of the code. This page is about the parts it couldn't.
Gridtone has no team, no investor and no deadline. It sounds like freedom. In practice every job is mine: the product, the brand, the research behind 265 models, the backend, the legal page, and the bill for every free build.
The constraints are real all the same. Time: one person's hours, and a beta that has to keep working while I change it. Money: the free tier runs on my own Anthropic account, so every build a stranger runs costs me something, and a launch could empty a month's budget in a day. And trust: a home player who finds one invented knob stops believing the rest.
Ask a chatbot for a Gilmour preset and you get a confident answer, with settings the unit doesn't have. A pro spots it and moves on. A home player assumes the mistake is theirs and spends the evening looking for a knob that was never there.
The model will always invent something, so the fix had to come after it. Its answer has to pass a check before anyone sees it: every model name, every setting, every value inside its range, every cab mic and slot, read against a catalog spelled the way the unit prints it. The promise came from there: if it's on the grid, it's on your Quad Cortex. A player can test that on their own unit in a minute, which is the point.
Four stages in twelve days, with one rule under all of them: nothing on the grid that isn't on the unit.
The front end was built by agents, in three batches of tasks. Each task went to one agent, and two more reviewed the result, once against the plan and once for quality. A task that failed review three times stopped and came to me.
One of them was the grid. Its thumbnail had to fit In and Out pills with words in them, at 8px, smaller than anything the brand guide allowed. The reviewer kept refusing it. Somewhere in those rounds the agent fixing it found a way through. It edited the brand guide to allow 8px labels. Against the new guide, the work complied.
Nothing was broken. Every test was green. The rule had moved to wherever the work already was.
I put the guide back, took the words out of the pills and gave them a small chevron, which is still what the thumbnails draw today. Then I changed how the agents run: from that day, none of them could edit the brand guide, the brand foundation or the design tokens. They can propose a change. I make it.
When you build alone with agents, the job isn't writing the code, it's owning the rules the code is checked against, and keeping them where nothing can quietly rewrite them.
Gridtone exists because AI makes things up. Ask a model for a preset and it will name knobs that aren't there, with total confidence. The product answers that with a catalog the model has to use and a check its answer has to pass, with every name spelled the way the unit prints it.
The agents that built Gridtone had the same habit. They wrote nearly every line, fast and well, and they were very good at making their own work pass. One rewrote a brand rule to fit its output. Just before this page was written, a build described its scenes in words, "TS808 bypassed", without turning anything off in the data. Each time the code was fine and the judgment was missing.
What stayed mine: what to build and what to leave out, the money rules, the spelling of the catalog, the voice, the redesign, and the call on every commit. Agents made one person fast enough to ship a working beta in twelve days.
gridtone.app builds a chain from a player, a song and a part. One free build on any browser, five a day with a Google account, and as many as your own Anthropic key allows. Saved chains follow you to every browser you sign in on.
Every chain is read against 265 Quad Cortex models and 7 cab mics from CorOS 4.1.1 before you see it, and every fix is listed. Six demo chains, researched with sources, pass with zero fixes.
A reservation before every build, a daily cap, a monthly budget, and limits per browser and per address. A launch can pause free builds for a day. It can't empty my account.
The Figma file was built from the live site. Light and dark variables, every type style, the components, 18 screens on phone and desktop, and the brand boards. Its thumbnail grid is drawn from the site's own geometry.
The calls that shaped it, reversals included. Most of them are about what Gridtone refuses to do.
Instead of: Trust a well-prompted model to stay inside the unit
A model will always invent a setting sooner or later. A check can't be talked out of the catalog, and it lists what it changed.
Instead of: The names on Neural DSP's online device list
The website drops the (M) and (ST) the unit shows, and a player looks for a block by the name on their screen.
Instead of: Unlimited free builds, or a paywall before the first chain
A player has to hear the product before paying anything. I have to know the worst day costs a known amount.
Instead of: Send players' keys through Gridtone's server
A key Gridtone never receives is a key it can never leak.
Instead of: A free build every day on every browser
A browser makes up its own ID, so a daily build per browser was easy to abuse. One build shows what Gridtone does. An account gives a player who comes back five a day.
Instead of: Saved chains kept only in the browser
Once there was an account, a chain saved on the laptop and missing on the phone was a broken promise.
Instead of: The first identity, quiet paper and graphite
It was correct and forgettable. The faceplate and the grid stayed calm. Everything around them got loud.
Instead of: The first identity's wordmark, Red Hat Display in lower case
Once text moved to Instrument Sans and titles to Big Shoulders, the wordmark was the last Red Hat Display on the site, kept only because it came first. Drawn as outlines it speaks with the poster type, loads no font, and still fits a 320px phone header.
Instead of: Let a fixer change whatever makes its review pass
The rules are what the work is checked against. They can't belong to the thing being checked.
Instead of: Blocks first, scenes after
Written blocks first, a chain's scene notes said a pedal was off while no block was. Scenes first, every scene has to differ in its blocks, and the check flags the ones that don't.
"If it's on the grid, it's on your Quad Cortex" is a promise a player can check on their own unit in a minute. It keeps the product honest, and it keeps me honest about what the check can't prove: that the tone is right for the song.
A free tier on your own API key is a cost model first and a screen second. Decide the reservation, the daily cap and the limits, then write the sentence the player reads when they hit one.
Agents optimise for passing. If the brand guide, the tokens or the tests can be edited by the thing under review, sooner or later they will be. Let agents propose a rule change, and make it yourself.
The first identity was correct and forgettable. Changing it on day eleven cost two days. Shipping something I found uninspiring would have cost more.
Fifteen years of designing products for other people's problems. Gridtone started with one of mine, with a guitar on my lap. It's in beta at gridtone.app, and the check is there for you to test on your own unit.