The research behind the balance

Selftone is a relaxation and self-reflection tool. The US FDA’s general wellness guidance uses software that plays music to help people relax as an example of a general wellness product. General Wellness: Policy for Low Risk Devices - Guidance for Industry and Food and Drug Administration Staff (opens in a new tab)

Your voice carries measurable information

Pitch, loudness and tone colour can all be measured from a recording, and researchers study these features closely. Selftone uses pitch to map the sound of your recording onto the twelve musical notes.

1. Researchers define and measure acoustic features of the voice.

   “In the context of voice, a vocal biomarker is a signature, a feature, or a combination of features from the audio signal of the voice that is associated with a clinical outcome”

   Open source: Voice for Health: The Use of Vocal Biomarkers from Research to Clinical Practice (opens in a new tab) Checked 2026-10-08

2. The pitch of the voice (its fundamental frequency, F0) is measurable and changes with circumstances such as stress.

   “The meta‐analysis showed a significant increase in F0 after stress (SMD = 0.5504, 95% CI [0.3014, 0.7995], p < 0.001) with substantial heterogeneity”

   Open source: The Fundamental Frequency of Voice as a Potential Stress Biomarker: A Systematic Review and Meta–Analysis (opens in a new tab) Checked 2026-10-08

Music and relaxation

Listening to music is one of the best-studied ways to unwind. These studies are about music in general, not Selftone in particular.

1. A systematic review of randomised trials found music interventions reduced both physical and psychological measures of stress.

   “Results showed that music interventions had an overall significant effect on stress reduction in both physiological (d = .380) and psychological (d = .545) outcomes.”

   Open source: Effects of music interventions on stress-related outcomes: a systematic review and two meta-analyses (opens in a new tab) Checked 2026-10-08

2. In a lab study, listening to music affected the body’s stress response.

   “Our findings indicate that music listening impacted the psychobiological stress system.”

   Open source: The Effect of Music on the Human Stress Response (opens in a new tab) Checked 2026-10-08

3. People reported feeling less tense after a singing-bowl sound meditation. This was an observational study without a control group.

   “As compared with pre-meditation, following the sound meditation participants reported significantly less tension, anger, fatigue, and depressed mood (all P s <.001).”

   Open source: Effects of Singing Bowl Sound Meditation on Mood, Tension, and Well-being: An Observational Study (opens in a new tab) Checked 2026-10-08

A kind sentence, out loud

Each day Selftone offers a short, positive sentence to read. Gratitude exercises are well studied; the effects are real but small.

1. A meta-analysis across cultures found gratitude exercises led to small increases in well-being.

   “we found that gratitude interventions led to small overall increases in well-being, Hedges’ g = 0.19, 95% CI [0.15, 0.22].”

   Open source: A meta-analysis of the effectiveness of gratitude interventions on well-being across cultures (opens in a new tab) Checked 2026-10-08

2. Regularly noting things you are grateful for was linked to more positive mood.

   “The effect on positive affect appeared to be the most robust finding. Results suggest that a conscious focus on blessings may have emotional and interpersonal benefits.”

   Open source: Counting Blessings Versus Burdens: An Experimental Investigation of Gratitude and Subjective Well-Being in Daily Life (opens in a new tab) Checked 2026-10-08

Small daily habits

Streaks and reminders exist to make a calm minute easy to repeat. Habits take time, and that is fine.

1. In a well-known study, new healthy habits took a median of 66 days to feel automatic, ranging from 18 to 254 days.

   “Lally et al. [ 5 ] examined the formation of healthy eating, water consumption or exercise habits and reported that the median time to reach 95% automaticity was 66 days (range: 18 to 254 days).”

   Open source: Time to Form a Habit: A Systematic Review and Meta-Analysis of Health Behaviour Habit Formation and Its Determinants (opens in a new tab) Checked 2026-10-08

2. Seeing an unbroken streak made people more likely to keep going.

   “In seven studies, we find that intact streaks highlighted via behavioral logs increase consumers' subsequent engagement in that behavior, relative to when broken streaks are highlighted.”

   Open source: On or Off Track: How (Broken) Streaks Affect Consumer Decisions. (opens in a new tab) Checked 2026-10-08

Twelve notes, and why 432 Hz

Selftone uses the twelve notes of the chromatic scale, the system behind most Western music. Each note’s complementary partner sits six semitones away. The tones are tuned with A at 432 Hz rather than the usual 440 Hz because we like how it sounds; research finds little evidence that any particular tuning has special effects.

1. Modern tuning divides the octave into twelve equal steps.

   “The most common equal temperament represents the octave as 12 exactly equal semitones.”

   Open source: Equal temperament (opens in a new tab) Checked 2026-10-08

2. The maths of equal temperament was worked out in the late 1500s, credited to Zhu Zaiyu in China and Simon Stevin in Flanders.

   “The two figures frequently credited with determining how to calculate equal temperament are Chinese mathematician and theorist Zhu Zaiyu (also romanized as Chu-Tsaiyu, Chinese: 朱載堉) and Flemish scholar Simon Stevin.”

   Open source: Equal temperament: History (opens in a new tab) Checked 2026-10-08

3. A = 440 Hz was recommended as a standard as early as 1834.

   “In 1834 Johann Heinrich Scheibler who had developed a pitch measuring device, the tonometer , recommended the pitch of A = 440 vibrations per second to the Stuttgart Congress of Physicists.”

   Open source: Fact Check: Tuning Standard Of A = 440 Hz Was NOT Driven By Nazis And Rockefellers, Nor By 'Desire For Discord' (opens in a new tab) Checked 2026-10-08

4. A music psychologist finds little scientific support for special effects of specific frequencies.

   “Although the concept of cosmic alignment is intriguing, there’s little scientific support for the idea that specific frequencies have any magical effect on wellbeing.”

   Open source: Does 432Hz tuning improve your wellbeing? A music psychologist unpacks the evidence (opens in a new tab) Checked 2026-10-08

How Selftone builds your balancing tracks

• Your recording is analysed for the strength of each of the twelve pitch classes (C, C♯, D … B) across the octaves your voice covers.
• Your three strongest notes and your quietest note are each paired with their complementary partner, six semitones away.
• Those four partner notes become your four tracks of about three minutes each, designed to balance your personal sound pattern. The tones are tuned with A at 432 Hz, a sound we like, under the sound style you pick.