Why I Built JammLab

I've been a professional guitarist for about ten years, and I still am. Three years ago I also started learning to code. JammLab is a browser-based chord chart tool that plays back real instrument samples, and it came out of a problem I had back when I was still a student. I wanted to practice improvising over very specific chord progressions, with real-sounding backing tracks, and there was no good way to do it. So I built one.

This is the short story of why.

Practicing harmony is harder than it should be

At nineteen I started studying guitar at Otsakool in Tallinn, a music school many Estonian musicians have passed through. It didn't take long to understand the real difference between a beginner and a professional player. When it comes to improvising, a beginner noodles pentatonic shapes but a professional understands the harmony underneath the solo. They know what chord they are playing over and exactly where they are in the progression.

This matters most when a song stops being simple. As long as everything stays diatonic, you can get away with a lot. But the moment a progression reaches outside the key, your ears and your fingers need to know what is coming.

Take "Creep" by Radiohead for example. In G major, the third chord is a B major — a secondary dominant, the V of vi. It pulls hard into the relative minor. If you are soloing over that song and you don't hear that B major coming, your solo will fight the harmony instead of riding it. A good player knows the secondary dominant is there and leans into it. That is the difference between notes and music.

So I wanted to be ready for those moments. I wanted to drill them.

My actual practice setup was bad

Here is how I practiced specific progressions back then.

YouTube is full of backing tracks. Every key, every style, endless options. But if I wanted to work on one exact progression not a generic 12-bar, but the specific changes I was stuck on there was nothing. So I would play the chords myself, record them into my phone's voice memo app, and then play my solo over that recording.

It worked, technically. You can probably imagine how it sounded: a guitar recorded through a phone microphone, looping back at me while I tried to find musical lines over the top. The recording did the job, but there was zero musical pleasure in it and constantly restarting the loop was its own kind of annoying. Practicing should not feel like fighting your own tools.

There was also iReal Pro. I want to be fair here, because iReal Pro is genuinely good and it has earned its huge, loyal following. Its biggest strength is the enormous catalogue of styles and songs. But for what I needed, two things got in the way: building my own progressions from scratch was slow and fiddly, and the playback didn't sound good enough to be worth the time I spent setting it up. The sounds were synthetic.

Neither option was built for the thing I actually wanted: take one progression, make it sound like a real band, and then live with it. Slow it down, speed it up, move it to another key, until it was under my fingers.

Years later, I went looking for a real problem to solve

When I started learning to code three years ago, I was fairly sure my music and my new path would never really overlap. I've now been in IT for a couple of years, while still playing.

At the start of 2026 I wanted to build something in my free time after work, and I asked myself a simple question: what is a real problem worth solving? Not an invented one, a problem I had actually lived with. It took me straight back to those years of serious practice. I would have been genuinely happy if an app like this had existed while I was studying. That was the moment JammLab started.

What JammLab actually does

The idea is simple: a chord chart tool that sounds like a band, and that you build yourself, in any browser.

You enter a progression bar by bar. The interface is fast enough that building a chord sequence takes a minute, not a fight and that speed turned out to matter more than I expected, in a way I'll come back to. Then you press play, and the backing is built from real recorded instrument samples. It sounds like musicians, not like a synthetic preset. That was the whole point — getting it to actually sound like a band.

And then the part that, for me, is the real reason this is better than a phone recording or anything I had before: control.

• Change the key with one click. If I want to learn a progression in every key (which is exactly how you internalize something like a secondary dominant move), I don't rebuild anything. One click and the whole chart transposes.
• Change the tempo with a few clicks. If I'm drilling a fast passage, I slow it right down, get it clean, and bring the speed back up. Right now the range runs from 51 to 190 BPM. That depends on the style, so it may differ as new ones are added.

The combination of fast to build, real-sounding, and instantly adjustable in key and tempo is the thing the phone recorder and the old tools never gave me.

A separate view for reading on stage

There is one more piece, and it grew out of that same "building progressions is fast" idea.

Practicing at home and performing live are two different jobs. Because entering chords in JammLab is so quick and simple, you can write out whole songs, not just practice loops. And once a whole song is in there, you can read it on stage like sheet music. So there is a clean chart-reading view for exactly that. It's the same chart, doing a different job: drilling at home, then reading live.

Where it is now

JammLab already has a catalogue of over 2,900 charts, works in all twelve keys, and currently covers the Rock style, with Funk coming up next and Jazz planned after that. It runs in the browser, and right now it's completely free while it's in early access.

That's the whole story. I built the tool I wish I'd had at nineteen, recording chords into my phone and wishing they sounded like a band. If you've ever done some version of that — fought your tools instead of practicing, that's exactly who I built this for.