How Klang.io is digitizing the music world with AI
It all started with a simple request: Sebastian Murgul’s little sister wanted to play a melody from her electric piano, but there was no sheet music. What followed was a detour via an oscilloscope app, laborious frequency measurements and handwritten notation on paper. But this frustrating experience gave rise to a business idea: Klang.io.
The Karlsruhe-based start-up is dedicated to automated music transcription and uses artificial intelligence to transform audio recordings into readable sheet music in just a few seconds. This elegantly solves a problem that has always plagued musicians – while professional transcribers still need around eight hours to transcribe a four-minute piano piece, Klang.io can do it in a matter of seconds.
From KIT student to founder
The story of how Klang.io came about reads like a typical Silicon Valley start-up tale – except that it takes place in Karlsruhe. “The idea for klang.io came from a personal experience around ten years ago,” Murgul tells us in an interview. Back then, as an electrical engineering student at KIT, he used an oscilloscope app, converted measured frequencies into pitches and laboriously wrote them down on music paper. “I asked myself the question: couldn’t it be easier?”
The tinkering began, and by early 2018 he had developed his first prototype, which he put online for free. “The response was overwhelming and showed me that there was a real need.” The next logical step was to found a company – with active support from the Karlsruhe start-up scene. “I found support at the KIT-Gründerschmiede, the CyberForum and the Pioniergarage. There, I received valuable help with the challenges of founding a company and got to know many inspiring founders, consultants and mentors who are still with us today.”
Learnings of a technician
But the path was not without its hurdles. “Setting up a company is not part of an electrical engineering degree,” reflects the founder today. “I was well prepared technically, but completely inexperienced in entrepreneurial matters. As a result, I started out quite naively and tried to manage a lot of things on my own.”
The most important realization: “I quickly learned that you can’t do everything yourself. The most important step was to gather the right people around me: my smart and always well-structured co-founder and CTO Alex Lüngen, our great team and mentors that we met through the CyberForum, and last but not least our tax advisor. Without them, the road would have been much rockier.”
AI technology meets musicology
At the heart of Klang.io is a unique AI system that was developed before the ChatGPT hype. “When we founded the company, it was before ChatGPT, when the first AI software libraries were just emerging. We recognized early on that deep learning could be an exciting solution for music transcription,” explains Murgul, who dedicated his bachelor’s, master’s and doctoral theses to this topic.
The way it works sounds complex, but it is elegantly thought out: “In principle, our system works like this: First, we convert the incoming audio into a spectrogram. This two-dimensional image shows the time on one axis, the frequency on the other, while the brightness indicates the volume. We then apply self-developed methods from image recognition and speech models to extract pitches, rhythm and harmonies.”
The final step combines this information with a language model “that depicts the musical ‘grammar’ of the respective instrument, so that in the end a readable and playable sheet of music is created.”
One particular challenge lay in the procurement of data: “The biggest challenge lies in the availability of training data. Music copyright is a complex and sensitive issue. That’s why we developed processes to generate millions of synthetic music samples that we use to train our models.”
An app universe for every musical taste
Klang.io has developed into a comprehensive ecosystem. “We have been building our klang.io app universe for several years. This app universe includes apps for a wide variety of musical instruments, such as piano (Piano2Notes), guitar (Guitar2Tabs), vocals (Sing2Notes), drums (Drum2Notes), wind instruments (Wind2Notes) and strings (Violin2Notes).”
The reason for this specialization lies in the detail: “Because every musical instrument is special in some way and we have tried to take that into account. For example, the piano has sustain pedals, the vocals have different pitches and the guitar has its very own form of notation, the guitar tabs.”
The target group is deliberately broad and ranges “from musicians, from composers who use our tools to notate new compositions, to music teachers who use us in their lessons, to amateur musicians who use our tools to find the notes for their favorite song.”
The business model follows a well thought-out freemium approach: “The first 20 seconds of a recording can be transcribed free of charge. This is important because the requirements for music transcription are very diverse. Users can test whether our solution is suitable for their use case before deciding on a subscription.”
Karlsruhe as a springboard for start-ups
Even in the growth phase, Klang.io benefits from the lively Karlsruhe start-up scene and the local networking pays off: “We still benefit from the lively Karlsruhe start-up scene today. K3 helped us find an office, the usability test dinner helps us to make our apps more user-friendly, and we regularly exchange ideas with other founders in CEO and CTO circles. We also continue to receive support from KIT and HFM for research projects.”
Although rooted in Karlsruhe, Klang.io has had a global presence right from the start and has the most customers in the USA, Japan and South Korea, “followed by Germany and the UK.” The founder has clear ideas for the future of the location: “I would find it particularly exciting if more music tech start-ups were to emerge here. The music industry is often underestimated, but AI in particular is creating new opportunities and business models.”
Team culture with musical DNA
The Klang.io team is united by more than just their work: “We have a friendly, open and music-loving team culture. We all play instruments ourselves and know the problem of missing sheet music from our own experience. That connects us and makes it easier to work together.” The pragmatic approach also characterizes the way we deal with challenges: “Our team is very
The team is particularly proud of an important milestone: “The most important milestone for us was the step towards profitability. Apart from a small investment as part of Startup BW Pre-Seed, we have grown bootstrapped, i.e. without external financing.”
The path there was creative: “In the initial phase, we programmed websites for SMEs on the side to finance development. We were all the more delighted when we became profitable at the beginning of 2024, just a few months after our participation in ‘Die Höhle der Löwen’, meaning we were able to cover all our expenses from our turnover.”
The figures speak for themselves: “Today, users worldwide generate over 15,000 transcriptions every day. At the same time, our team has grown, our apps have been expanded and the quality of our transcriptions has improved significantly.”
The next development steps are already planned: “On October 6, 2025, we will launch our new AI models for multi-instrumental transcription. These include a rock model that recognizes lead and rhythm guitar, bass and drums from mixed songs, as well as a classical model that can transcribe complex ensembles of strings and wind instruments. Both models will be part of our Transcription Studio.”
Klang.io is an example of the digitalization of a traditionally analogue industry: “The music industry is still very paper-based in many areas and is not very digitalized compared to other industries. This is due to complex copyright law and a certain degree of technological skepticism in parts of the scene.”
More information can be found at klang.io. The apps are available for iOS, Android and as a web application.