Mirelo, an audio company that lets anyone generate perfectly synchronized sound effects for videos, has just raised about €35 million ($41 million) in a seed round, co-led by Index Ventures and Andreessen Horowitz, with participation from Atlantic.vc and TriplePoint Capital.
The Berlin-based startup was founded by two senior AI researchers who are also accomplished musicians, and who left big tech to build breakthrough foundation models in audio – one of the most emotionally resonant but technically underdeveloped areas of AI. The funding is a sign of a broader shift in creative expression, as AI tools empower more and more artists and designers to bring their ideas to life.
Sound has a unique power to influence our feelings and reshape how we experience reality. Yet while AI has transformed the creation of text, images and video, sound is yet to catch up. As a consequence, adding music and audio to visuals still involves creators and sound designers spending hours searching stock libraries and manually syncing effects.
Mirelo, founded in 2023, has responded to this challenge by developing its own cutting-edge foundation models for sound in videos. A user can upload any video, and in a matter of seconds Mirelo’s system produces matching audio for anything happening on screen. The ability to produce high-quality sound faster than real time becomes particularly important in a world of dynamic content, whether that’s AI-generated videos or adaptive gaming worlds that shift for each player.
“Think of the difference between talkies and silent films – video without sound has so much less feeling and atmosphere,” says CJ Simon-Gabriel, CEO, and co-founder. “Mirelo’s first step is about democratising access, empowering everyone to create the sound that their (AI) video deserves. But we’ll also empower professionals to rework audio, to do more of what they love, to be more expressive and imaginative in what they can achieve, while handling the boring stuff such as synchronization. Our bigger mission is to become the audio layer for all visual content across videos, gaming, social media, films and beyond.”
Mirelo’s founders, CJ, and Florian Wenzel, met as AI researchers at AWS Labs before starting their own company. CJ has a PhD in machine learning and causal inference from the Max Planck Institute, where he studied under renowned computer scientist Bernhard Schölkopf, and completed a postdoc at ETH Zurich. Florian, Mirelo’s CTO, has a PhD in deep learning from Humboldt University, and was a researcher at Google Brain.
Mirelo sprang from the pair’s shared passion for music and frustration with their field’s narrow focus on images and LLMs. CJ has a degree in piano, organ and composition from the Conservatoire in Strasbourg, and was very close to pursuing music professionally; he dreams one day of recreating the unwritten music of Mozart and Schubert. Meanwhile, Florian mixes music and plays electric guitar as a member of an electro band in Berlin.
A couple of weeks ago, the young company released a new, top-notch video-to-sound-effect model, Mirelo SFX v1.5, which can generate various soundtrack versions faster than real-time. It is available via their self-serve API and web-app, Mirelo Studio. Mirelo’s models are very lightweight, requiring 50 times less compute than typical LLMs, while also delivering superior quality to any competitor so far according to external evaluations.
“Sound is too often an afterthought in video production, yet it’s what determines whether a video or game truly resonates with its audience. Mirelo gives creators a new form of expression, letting them move faster and sound better,” says Georgia Stevenson, the partner at Index Ventures who led the investment. “The team led by CJ and Florian combines cutting-edge AI expertise with an unparalleled focus on audio’s emotional power. It is a combination that positions them to reshape how the world experiences sound.”
“To date, a16z has invested in multiple world-leading generative models each with a different focus area. Mirelo is tackling one of the most technically challenging and least explored areas of generative media: a specialized model for sound effect creation.” said Guido Appenzeller, partner at Andreessen Horowitz. “CJ and Florian have assembled a research-driven team whose breakthroughs in tokenization, data curation, and conditioning rival far larger efforts and we’re excited to back Mirelo as they scale their technology for the next generation of video models.”
Read the orginal article: https://www.eu-startups.com/2025/12/berlin-based-mirelo-raises-e35-million-seed-round-co-led-by-index-ventures-and-andreessen-horowitz/
