About Chord Trainer

Chord Trainer is built by Aaron Technologies OÜ, an Estonian technology company focused on APIs and tools for modern music education.

Our Company

Aaron Technologies OÜ is a private company registered in Estonia (Registry Code: 17336129, VAT ID: EE102955587). We develop infrastructure and tools for music education and AI-powered travel validation.

Our flagship project is Chord Trainer — a speed-training tool that helps jazz pianists master voicings in all 12 keys. Built on modern web technologies, Chord Trainer features MIDI recognition, ii-V-I progressions, progress tracking, and guided practice plans.

We're based in Tallinn, Estonia, with operations in Berlin, Germany.

Why We Built Chord Trainer

Jazz piano education requires repetition and muscle memory. Students know the theory — extensions, voicings, alterations — but struggle to play changes fluently across all keys. There was no dedicated tool for this specific, measurable speed drill. So we built it.

Founder & CEO

Aaron Julius Pfützner

Founder & CEO of Aaron Technologies OÜ. Background in IoT, embedded systems, and full-stack development. Passionate about building tools that solve real problems in music education and developer infrastructure.

Email LinkedIn GitHub

Get in Touch

For Chord Trainer inquiries:
info@jazzchords.app

For partnerships or other matters:
admin@must-seen.com

Phone:
+49 15679 706761

Company Details

Legal Name: Aaron Technologies OÜ

Registry Code: 17336129

VAT ID: EE102955587

Legal Form: Osaühing (Private Limited Company)

Address: Sepapaja tn 6, 15551 Tallinn, Estonia

Trade Register: Estonian Commercial Register

Management: Aaron Julius Pfützner (CEO)