Klavissimo.app Reviews and Details

Questions & Answers

1. What makes Klavissimo.app unique?

   It listens to the instrument, not to a microphone or a mouse click. Your digital piano is connected over MIDI, so Klavissimo knows exactly which key you pressed, when, and how hard — and can tell you which individual notes and which bars still need work, instead of giving you one score at the end.

   It also runs with no account at all. There is no sign-up, no profile, no cloud sync by default: your practice history lives in your own browser storage on your own device.

2. Why should a person choose Klavissimo.app over its competitors?

   Three reasons, all of which you can verify before paying anything:

   • No account. You open the page, plug in your piano and play. Nothing to create, nothing to cancel, nothing to delete afterwards.
   • Practising is free and stays free — the full note-by-note feedback is in the free tier. The paid plan adds the AI tutor, not the core.
   • Your playing stays on your device. The AI tutor is optional and switched off by default; when you turn it on, only note-free metadata is sent, never your sheet music or your recordings.

   You can also bring your own sheet music as MusicXML and practise that, rather than only a fixed in-app catalogue.

3. How would you describe the primary audience of Klavissimo.app?

   People who already own a digital piano or keyboard with a MIDI or USB connection and want to practise on their own — adult beginners and returners, and children practising at home. Music teachers are a second audience: a class licence lets a teacher follow their pupils' practice without the pupils needing accounts.

   It is not aimed at people without an instrument: without MIDI you can look around, but the core of the product is the connected piano.

4. Which are the primary technologies used for building Klavissimo.app?

   TypeScript, Next.js 15 (React 19), Web MIDI API, Web Audio API with AudioWorklet, OpenSheetMusicDisplay for notation rendering, SpessaSynth for SoundFont playback, Fastify and PostgreSQL on the server side.

5. What's the story behind Klavissimo.app?

   I watched my son learn the piano on his e-piano at home. Between the lessons at his music school lies the practice week — that is where progress is actually made, and that is exactly where nobody is listening. The idea grew from there: his sense of rhythm would come along faster if something could show him, playfully, where he had been off the beat, and then challenge him to do it better.

   The instrument already says all of it. A digital piano sends every key, the precise moment it was pressed and how hard — everything you would need to give that kind of feedback. Klavissimo is built around exactly that. It is made and run by one person in Austria, in German and English.