Music Generation Application based on Real-time Biometric Data



Yudemon uses generative music and soundscapes, conditioned on real-time biometric data, to elevate happiness, performance, and overall well being. Yudemon improves upon existing practices and protocols in the areas of mindfulness and biofeedback, and also enables entirely new immersive and highly personalized experiences.

Heart rate variability (HRV) biofeedback training has shown tremendous results, both in treating mental issues but also in optimizing the performance of healthy minds. At its core, HRV biofeedback uses a breathing technique called resonance breathing in which breathing at a certain personalized rate stimulates the autonomic nervous system. On the inhale the heart accelerates, on the exhale it slows down, leading to smooth heart rate oscillations and a large HRV, training the heart’s adaptability and the entire body’s stress response. However, the feedback aspect of the current biofeedback systems is very primitive, using only simple visual breath timers and a real-time display of heart rate and HRV. It’s time to take this to the next level, and sound is the key.

The use of sound in meditation and mindfulness practices and protocols like HRV biofeedback training is limited to static soundscapes. Yudemon is unique in that it creates a tight feedback loop, where music is created and modulated in real-time based on biodata, like ECG, and its impact can be monitored, evaluated, and constantly refined through the same data stream.

Practicing with Yudemon is like taking your autonomic nervous system to the gym for a focused and highly personalized training session.


Max Frenzel and Nao Tokui, Yudemon’s founders, have been interested in taking control over their physiology — and in turn their minds — for a long time. In 2020, during a particularly stressful time, we came across HRV biofeedback training and found its impact transformative.

The name Yudemon comes from the Ancient Greek word daimon (pronounced démon), which is closely related to the human soul and spirit, but also contains a divine and super-human element. It was seen as a spiritual driving force for great achievements and genius, a strong unrest deep in our soul that forces us to explore our full potential and the unknown within us. 

Functional music, i.e. music created for a specific purpose such as stress-relief, focus-boost, or sleep-aid, has seen accelerating growth over the past few years. Yet most players in the space approach functional music from a purely ambient or background music perspective, something that passively and often subconsciously happens to the listener. With Yudemon we wanted to take a different approach by offering an active practice based on full engagement and participation of the listener. 

iOS App

To start providing value to real users even while the underlying technology is still in development, an iOS app was created which functions as a simple but visually and sonically compelling breath timer, dramatically improving on the aesthetic and functionality of other existing breath timers for HRV biofeedback.

A generative visual that expands and contracts at the breathing rate guides the practitioner in the breathing. This is further enhanced and accentuated by a specifically designed soundscape playing in sync with the visual timer. Both visual and sonic guidance are highly customizable.

The app has not yet been publicly released, but is available to beta testers. If you would like to join the group of testers, please use the contact page on www.yudemon.com.


The soundscape used in the app was specifically designed for HRV biofeedback training and resonance breathing. The musical elements were tuned to the breathing frequency and follow the inhale / exhale cycle, aiming to stimulate the sympathetic nervous system (“fight-or-flight”) on the inhale, and then parasympathetic nervous system (“rest-and-digest”) on the exhale, mirroring the effect of the breathing itself and aiming to enhance the HRV increasing effect.

The soundscapes have been released for a range of breathing frequencies.


Prior to developing the user-facing iOS app, a web-based internal development prototype has been built and maintained in order to test and development Yudemon’s core technology and to perform experiments and studies that inform the future direction of the mobile app.

The development prototype consists of two different modes, Session mode and Analysis mode.

Session Mode

Session mode is where the actual practice happens. A user’s electrocardiogram (ECG) data is streamed in real-time from an ECG sensor, for example the popular Polar H10 chest strap, via bluetooth and displayed at the top of the screen. The derived heart rate (HR) and heart rate variability (HRV) are also displayed. In addition, a visual breath timer shows the practitioner when and how to breathe. This is also synced with a specifically designed soundscape that gives a sonic indication of the breath cycle.

Analysis Mode

Analysis mode allows a user to view and analyse their completed sessions. One key aspect in HRV biofeedback is the notion of a “resonance frequency,” the optimal rate at which to breathe for the largest heart rate variability. This rate varies from person to person (with a population mean of around 6 breaths per minute). Analysis mode allows for identifying this optimal breathing rate.


Using the development prototype, we ran several self-experiments on various aspects of HRV biofeedback training.

Experiment 1. Resonance Frequency

As alluded to above, the rate at which the breathing is practiced is important for its effectiveness. Most existing apps determine the resonance frequency through a single session in which they ask the user to breathe at 5, 5.5, 6, 6.5 and 7 breaths per minute for a set duration and then choose the one with the highest HRV. Not only is such a single session approach highly susceptible to fluctuations, the resolution of 0.5 breath/min intervals is also far from optimal.
To determine the resonance frequency with far more accuracy and confidence, we used the Yudemon app for a self-study in which we practiced at all frequencies between 5 and 6.5 breaths/min in 0.1 increments, for 30 minutes at each frequency, 8 hours in total, over the course of ten days. The results showed that the subject’s personal resonance frequency, which achieved the highest HRV, lies with fairly high confidence between 5.3 and 5.4 breaths/min.

Experiment 2. Inhale/Exhale Ratio

Just like the overall duration of a breath cycle, so too does the relative length of inhale and exhale play a role on the effectiveness of the practice. Usually the cycle is split into 40% inhale and 60% exhale duration, but no convincing data appears to exist to back up its optimality.
In a second experiment, we studied the effect of different ratios on the subject, again collecting and analyzing multiple hours of data. The results showed a moderate correlation between HRV and inhale/exhale ratio, with an optimal ratio of around 35% inhale and 65% exhale for the test subject.

Experiment 3. The Effect of Sound

Finally, testing the assumptions behind one of Yudemon’s unique features, a soundscape was specifically designed for HRV biofeedback training and again tested over several hours of practice through analyzing the corresponding HRV data.

The version of the soundscape that contained both time-signaling rhythmic and melodic elements that indicated the inhale and exhale phases, as well as resonant part that gave a underlying ambience tuned to the specific breathing frequency, showed an impressive 20% increase in HRV compared to a baseline of practicing in silence.




  • Project Lead and Execution

    Max Frenzel

  • Funding

    Qosmo, Inc.

  • Logo Design

    Niko Lanzuisi

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