Live timing feedback and session review for electronic drums

Connect your electronic drum kit by USB, see whether each hit is early or late as you play, then look back at the session to find what to practice next.

GrooveDojo reads the notes your kit sends over MIDI, in your browser. It’s free, with no account required and nothing to install.

Open GrooveDojo

What you need

A kit that sends MIDI over USB. GrooveDojo has been tested with a Roland TD-27KV2. Many other modules are listed from their makers’ documents but not tested yet (the list).
A browser that can receive MIDI. Kit input has been tested in Chrome on a Mac, in Firefox on a Mac and in Chrome on an Android phone. Safari, and every browser on iPad and iPhone, can’t receive MIDI, so a kit can’t connect there.
Wired headphones, speakers or your module for the click. Bluetooth adds a delay that’s long and keeps changing, so timing results would be off.

Compatibility says what has been tested, and what hasn’t been yet.

Connecting your kit

Connect the module to your computer or phone with a USB cable.
Open GrooveDojo and choose Connect kit. Your browser asks whether GrooveDojo may use your MIDI devices.
If your module reports a model GrooveDojo knows, it uses that kit’s factory note map. If it doesn’t, GrooveDojo asks “Which kit is this?”. Until you answer, you play along as usual, with nothing scored.
In Settings, Drum mapping, the pad check shows which drum each pad lands on, and MIDI learn fixes any that are wrong.
In Settings, Timing, tell GrooveDojo how you listen.

While you play

Your kit sends a MIDI note for every hit. GrooveDojo matches each hit to a note of the groove and compares its time with the click. The groove can be one of the built-in exercises or one you write in the groove editor.

Marks on the notation. Each hit appears as a disc behind its note, moved by its timing. Within your Timing mark window (Settings, Practice) it stays gray. Outside it, it shows early or late.
After each run, you see which hits were early or late, by how much, and on which drum, with each drum’s details. Missed notes, notes played on the wrong drum and extra hits are counted too.
The hi-hat: open and closed come from the notes your kit sends. After a short calibration of the pedal in Settings, Drum mapping, they come from the pedal itself, half-open included.
What your kit can’t send isn’t judged. If its map has no rimshot or ride bell, say, those notes are checked by the drum only, and the results say so.

After you play: the session review

When you choose End & review, GrooveDojo looks at the whole session, every run at every tempo, and answers a few practical questions.

How did the session go?

Your practice opens the review: how long you practiced, how many notes you played, how evenly each drum played, and which loops were consistent, your best and roughest marked to listen to. Since last time compares the session with your last one on the same groove and kit, at the tempos you played both times. Went well lists up to three things the numbers show held up, or nothing.

The top of a session’s review on a phone. Your practice: 2 min of practice, 2 runs from 80 to 90 BPM. Notes played, 95.8%, 668 of 697 notes. Timing spread, ±6 ms around your usual timing, with a bar for each drum, the kick and snare widest. Consistent loops, 1 of 17, the fastest at 90 BPM, with a square for each loop of each run and the best and roughest labeled. Below, Since last time says this is the first session with this groove. — Your practice: notes played, each drum’s timing spread, and a square for every loop.

Was I ahead of or behind the click?

More detail, at the end of the review, shows where each drum sits against the click, one tempo at a time. A kick that sits behind the beat, or a hi-hat that varies more at the faster tempo, stands out there, and each run’s own results are there too.

Timing against the click at 90 BPM, one row for each drum: Hi-Hat, Tom 1, Tom 2, Snare, Floor Tom and Kick. Every hit is a dot against the click, gray within ±30 ms, blue when earlier and orange when later, with a line at each drum’s middle. Each drum’s middle sits between 10 and 20 ms behind the click. — See how each hit lined up with the click, grouped by drum.

Which bars should I practice again?

The review looks for what came back loop after loop: a note you often missed, one that was early or late each time, or one whose timing kept changing. What to improve shows each one in the notation, at the tempos it happened. Practice this loops just those bars, and Before and after compares that practice with your session. A session with nothing that kept coming back has nothing listed.

What to improve in a session’s review: a two-bar groove in notation with three notes numbered as problems, the kick on 3 & of bar 1 later than usual, a hi-hat in bar 2 often missed and the snare on 4 of bar 2 earlier than usual, with buttons to show one drum or one tempo at a time, or a list of notes. — What to improve numbers the notes that kept slipping, on the groove’s own notation.

The first problem’s card, Start here: Your kick on 3 & lands later than usual at 90 BPM, with bar 1’s counts and its 3 & outlined. Its Listen is playing, with Stop, Yours and As written, 100%, 75% and 50%, and Click, and a note that these are your hits on GrooveDojo’s drum sounds, not a recording. Under it, 80 BPM had not enough passes and 90 BPM tends later. It suggests practicing at 80 BPM, looping bar 1, with a Practice this button. — Listen to an example, then use Practice this to loop the bar.

What did I actually play?

Listen back to a problem’s bars, your best and roughest loops, any loop from any run, or both sides of Before and after, played on GrooveDojo’s own drum sounds. Switch between Yours and As written to hear what you played against what’s written, and slow it down to 75% or 50%. While it plays, the notation shows the loop you’re hearing, with its marks.

This isn’t an audio recording of your drums. GrooveDojo replays the MIDI notes using its own drum sounds.

Two cards to play back: Best loop, run 2, loop 7, with no mistakes and your most even timing, and Roughest loop, run 2, loop 1, with 6 missed and 1 extra hit. Under them, a chip for each run, the loop chosen, Listen with Yours and As written, the speeds and Click, and the loop’s two bars in notation with every hit marked. — Listen back to your best and roughest loops, with timing marks shown on the notation.

Earlier sessions stay in your practice history, saved in your browser. To come back to a groove on a given day, Add to plan… in its review puts it in a practice plan.

What the numbers can and can’t tell you

A hit’s time is when it reached GrooveDojo. That includes the time your kit, its cable and your computer take to deliver it, which GrooveDojo doesn’t measure or remove. So a single number, such as “12 ms late”, can carry a steady error from your setup. How even your hits are, and how runs on the same setup compare, tell you more than one number. The review’s findings come from what repeats across a session, so they’re worth checking against how the bars felt and sounded, not taken as a verdict.

Timing results are practice feedback, not laboratory measurements (more on their limits). How drum timing is measured follows a hit from your pad to the result, and says which delays GrooveDojo accounts for and which it can’t.

No electronic kit?

You can still practice in GrooveDojo with the click and the notation, on an acoustic kit or a practice pad. There’s no timing feedback without a kit, but your practice time is kept (practicing without a kit).