In February 2019, Kim Hyuk Gun (김혁건), the vocalist of THE CROSS (더크로스), received his Ph.D. from the Department of Applied Arts (Practical Music major) at the Graduate School of Kyung Hee University. His 288-page dissertation, 「횡격막 마비군과 비마비군을 통한 복식호흡과 발성법 연구」, is an experimental study of how much abdominal breathing helps in singing high notes.
This article is for students who sing in popular-music programs. It sets out the study's questions, participants, methods and conclusions in one place, and lays out the map of the 24-part series to come. Each part is paired with one of the vocal lessons Kim Hyuk Gun taught — eight from Season 1 and sixteen from Season 2, 24 in all.
01.A Vocal Study Written by a Singer
This dissertation is a study in which a singer who performs on stage tested the principles of his own voice through an experiment. The researcher is a rock vocalist who debuted in 2003 with "Don't Cry," and the singing lessons in the experiment used 24 videos of "Cross Kim Hyuk Gun Vocal Lessons," which he made himself.
The study was approved by the Institutional Review Board (IRB) of the Kyung Hee University Industry-Academic Cooperation Foundation and Office of Research (project no. KHSIRB-17-047). Participants were told the purpose, procedure and methods of the study, and only those who volunteered signed a consent form; they were told they could withdraw their consent at any time. The dissertation does not name the participants and refers to them only by letter.
The experiment ran for eight months, from October 2017 to May 2018.
02.The Six Chapters of the Dissertation
The dissertation has six chapters. First, here is which chapter this series reads in which parts.
| Chapter | Title | Printed pages | In this series |
|---|---|---|---|
| I | Introduction — research questions, research model, participants, methods, terms | 1–42 | Part 1 |
| II | Diaphragmatic paralysis caused by spinal cord injury | 43–62 | Part 1 (research background) |
| III | Scientific vocal technique — breathing, vocal organs, resonators, vocal methods | 63–124 | Parts 2–18 |
| IV | Respiratory rehabilitation and singing training — section 3, "Respiratory rehabilitation and vocal education" | 125–181 | Parts 7, 10–13, 16, 19–23 |
| V | Experiment and results | 182–217 | Part 24 |
| VI | Conclusion and discussion | 218–221 | Part 1 |
Chapter II is background for understanding the study's diaphragmatic-paralysis group. The dissertation notes that the diaphragm is controlled by the phrenic nerve, which arises from the third to fifth cervical vertebrae, and that it handles 70% of the inhalation function in a healthy person's breathing. One passage speaks directly to singing students: the dissertation explains that the diaphragm assists the work of the vocal folds, so the better you use the diaphragm, the less fatigue the vocal folds feel and the longer you can sustain and support the sound.
The first part of Chapter IV sets out the concept and types of respiratory rehabilitation as research background. This series does not cover that part separately; it reads the posture, correct breathing, support, pitch, nasal resonance, resonance methods and practice methods in section 3, "Respiratory rehabilitation and vocal education," from the point of view of singing practice.
03.The Two Questions the Study Asked
The line every singing student hears — "breathe from your belly" — connects directly to the question of this dissertation. Does abdominal breathing really help high notes? The dissertation divided this into two questions.
| Research question | Question | What was measured |
|---|---|---|
| Ⓐ | Does singing and breathing training have a positive effect on lung capacity? | Inhaled and exhaled volume |
| Ⓑ | Does forced abdominal compression (abdominal breathing produced by pressing on the belly) have a significant effect on vocal range? | Vocal range (measured with a tuner) |
The research model is simple. Before training, measure the amount of breath and the range; after training, measure again with the same tools and compare. The dissertation also set a third question about everyday indicators alongside range expansion, but this series reads mainly the breathing and range results that singing practice needs.
On the purpose of the study, the dissertation writes this: to measure the range when the diaphragmatic-paralysis group sings breathing on their own and when they sing with forced abdominal breathing, to find out how much abdominal breathing helps in singing high notes, and to find out how the range changes before and after singing lessons that train control of the vocal folds. Behind this lies one explanation of the diaphragm. We breathe without thinking about it, but because we can control the speed of our breath or hold it, the diaphragm is a voluntary muscle that can be moved at will and strengthened through training.
04.Eight People, Four Groups
The dissertation set up two groups side by side: people who cannot breathe abdominally on their own, and people who can.
| Group | Number | Make-up | Characteristic |
|---|---|---|---|
| Diaphragmatic-paralysis group | 4 | 2 trained singers · 2 non-majors | Cannot move the diaphragm on their own because of spinal cord injury, so active abdominal breathing is not possible (two or more years since onset) |
| Non-paralysis group | 4 | 2 trained singers · 2 non-majors | Can breathe abdominally on their own |
Because the diaphragmatic-paralysis group cannot tense the abdomen, the effect of "passive abdominal breathing" — pressing on the belly from outside to push the diaphragm up — can be seen on its own. With this method, the dissertation measured how abdominal pressure affects singing in the passaggio. People less than two years from onset were excluded to reduce the variable of natural recovery.
05.Three Kinds of Training and Ten Sessions
The experimental program had three parts.
- Ambu bag breathing training — after inhaling as much as possible on their own, participants had more air added with a 500cc manual resuscitator (Ambu bag) to expand the lungs.
- Forced abdominal compression — passive abdominal breathing in which both hands press hard on the belly to push the diaphragm up. In the non-paralysis group the abdominal muscles resisted by reflex, so this method could not be used; it was applied only to the diaphragmatic-paralysis group.
- Singing training — lessons centered on breathing and vocal technique. The goal was to carry high notes through the passaggio, the zone connecting the low and high registers, through a balance of force between the diaphragm and the vocal folds.
The singing training was given to the non-majors over ten sessions. In each lesson they watched videos from the 24-part "Cross Kim Hyuk Gun Vocal Lessons" together, practiced along and received feedback. Here is the dissertation's Table 5, reorganized for students.
| Session | Goal | Lessons (number · topic) |
|---|---|---|
| 1 | Understanding the basics of vocalizing · pre-measurement | 1-1 Correct abdominal breathing, vocal exercises · 2-4 Basic vocal exercises |
| 2 | Head voice and chest voice | 1-2 Head voice, vocal-fold closure, mix voice · 1-3 Resonance, head voice, chest voice · 1-6 Chest-voice technique, chest breathing |
| 3 | Vocal technique | 1-4 Vibration, vibrato · 1-5 Passaggio, support, pitch, resonance |
| 4 | Nasal resonance · pronunciation | 2-3 Nasal resonance · 2-5 Correcting pronunciation |
| 5 | The next step in vocalizing and breathing | 1-8 Connecting head and chest voice · 2-6 Abdominal breathing |
| 6 | Vocal technique | 1-7 Support, tone control · 2-8 Vibrato practice |
| 7 | Vocal technique | 2-9 Chest (full) voice · 2-10 Falsetto · 2-11 Half-falsetto, mix voice, vocal-fold closure |
| 8 | Understanding singing styles | 2-12 Resonance, raising your range · 2-13 Low notes · 2-14 Low-mid notes |
| 9 | Raising the range | 2-15 Raising high notes · 2-16 Shout technique |
| 10 | Review · post-measurement | 2-4 Basic vocal exercises · 2-11 Vocal-fold closure · 2-15 High notes |
Source: reorganized from Kim Hyuk Gun (2019), Table 5, "Vocal training program and lesson content." Ambu bag breathing training was done alongside in sessions 2–9. The links in the table are the edition the dissertation cites (re-uploaded in December 2012). Lesson videos are in Korean.
Measurements were taken in session 1 and session 10 with the same tools. Exhaled breath was measured with a peak flow meter, inhaled breath with an inspiratory meter with three chambers (700cc, 1300cc and 1900cc), and range with a tuner. When you sing a note, the tuner shows the pitch and how high or low it is as a number.
Following Scientific Pitch Notation (SPN), the dissertation calls middle C (C4) "2-octave C" and C5 "3-octave C."
06.What the Study Found
The results the dissertation reported come down to three points (group results).
- Breath increased. All four non-majors who received the ten sessions of singing and breathing training (two from each group) showed increased inhaled and exhaled volume, and the dissertation reported that the difference in breathing volume before and after training was highly statistically significant.
- Abdominal compression widened the range. In the diaphragmatic-paralysis group, passive abdominal breathing produced by pressing on the belly widened the range. After singing and breathing training, the range also widened in their own unassisted breathing, and the non-paralysis group's range widened with training as well. The change was larger among the non-majors.
- When the forces lose balance, the note breaks. When the exhaling force was too strong and the force closing the vocal folds was too weak, the note broke. Pushing breath hard is not, by itself, how high notes are made.
With this, the dissertation confirmed that abdominal breathing was an important factor in crossing the passaggio, and concluded that high-note progression and resonance in the passaggio are possible when the diaphragm, a breathing muscle, and the vocal folds are in balance. It also noted that, with only eight participants, the study is limited in how far its results can be generalized. The results in numbers are set out as group figures in Part 24 · Practice Routine and Experimental Results.
07.How to Use This Series in Practice
You can use the order the dissertation used in its experiment as your practice order.
- Write down your range before you start. With a tuner app, record the lowest and highest notes you can sing comfortably in SPN (for example, C5 = "3-octave C"). As in the study, you need a "before" to compare with an "after."
- Treat ten sessions as one cycle. Watch and follow the lesson videos in the order of the sessions in the table in section 05. Session 10 is for review and measuring again.
- Watch breath and vocal folds together. As the note-break result in section 06 shows, high notes come when the strength of the breath and the force closing the vocal folds match. Parts 2–4 (breathing) and Parts 5 and 6 (the balance between the vocal folds and the diaphragm) cover this balance in detail.
Ambu bag breathing training and forced abdominal compression were carried out as experimental procedures reviewed by a research ethics board. Do not turn them into exercises to try on your own.
The lesson to watch with this part is Season 1, Episode 5, "Singing Technique." Its description gathers five things in one video: support (restrained exhaling), pitch, the three elements of sound (breath, vocal folds, resonance), vibrato and passaggio. Marking where these five appear in the series gives you the series map.
| What the lesson covers | In this series |
|---|---|
| The three elements of sound — breath · vocal folds · resonance | Parts 2–4 · 5–8 · 9–11 |
| Vibrato | Parts 15 and 16 |
| Passaggio | Parts 17 and 18 |
| Support | Part 20 |
| Pitch | Part 21 |
08.The 24 Parts and Where to Go Next
| Part | Topic | Dissertation pages (printed) | Lesson paired with it |
|---|---|---|---|
| 1 | Study overview (this article) | 1–42 · 218–221 | Season 1 Ep. 5 Singing Technique |
| 2 | Understanding phonation and the role of breath | 63–66 | Season 1 Ep. 1 Breathing |
| 3 | Chest, rib and abdominal breathing | 66–69 | Season 2 Ep. 6 Abdominal Breathing |
| 4 | Lungs, diaphragm and breathing muscles | 70–81 | Season 1 Ep. 6 Chest-Voice Technique |
| 5 | The larynx and vocal folds | 82–88 | Season 1 Ep. 2 Head Voice |
| 6 | The balance of force between the vocal folds and the diaphragm | 88–92 | Season 2 Ep. 7 Releasing Throat Tension |
| 7 | Chest (full) voice — the sound made with the folds together | 23–29 · 88–89 · 176 | Season 2 Ep. 9 Chest (Full) Voice |
| 8 | Falsetto and registers | 23–29 · 116–122 | Season 2 Ep. 10 Falsetto |
| 9 | The resonators — mouth, soft palate and pharynx | 92–98 | Season 1 Ep. 3 Resonance Spaces and How to Use Them |
| 10 | The nasal cavity, sinuses and using nasal resonance | 95–99 · 161–162 | Season 2 Ep. 3 Nasal Resonance |
| 11 | Resonance methods | 163–164 | Season 2 Ep. 12 Resonance |
| 12 | Chest voice — lowering the tongue root, raising the soft palate | 174 · 177 | Season 2 Ep. 1 Chest Voice |
| 13 | Head voice — a bright "e" and the maschera | 23–29 · 175 | Season 2 Ep. 2 Head Voice |
| 14 | From bel canto to modern scientific vocal technique | 100–112 | Season 1 Ep. 8 Connecting Head and Chest Voice |
| 15 | How vibrato works | 113 | Season 1 Ep. 4 Vibration and Vibrato |
| 16 | Vibrato practice and dollyeonaegi | 113 · 176 | Season 2 Ep. 8 Vibration |
| 17 | Passaggio — the transition zones by voice type | 114–122 | Season 2 Ep. 11 Half-Falsetto |
| 18 | High notes and appoggio | 123–124 | Season 2 Ep. 15 High Notes |
| 19 | Posture and correct breathing | 146–156 | Season 2 Ep. 14 Low-Mid Notes |
| 20 | Support | 157–158 | Season 1 Ep. 7 Support and Tone Control |
| 21 | Pitch, range and interval practice | 159–160 · 164–169 · 174 | Season 2 Ep. 13 Low Notes |
| 22 | Diction — consonants and vowels | 178–179 | Season 2 Ep. 5 Correcting Pronunciation |
| 23 | Sing with your breath — other elements of vocal education | 170–175 | Season 2 Ep. 16 Shout Technique |
| 24 | Practice routine and experimental results | 182–217 | Season 2 Ep. 4 Vocal Exercises |
The next part is Part 2 · Understanding Phonation and the Role of Breath. Kim Hyuk Gun's voice and repertoire are in Kim Hyuk Gun's Voice: Three-Octave High Notes and Hard Rock Roots, and the path he has taken is in Kim Hyuk Gun: Official Profile and Name Guide. The full set of vocal lessons is on the 뮤토리 (Mutory) YouTube channel.
The record of a singer who sang above the third octave on stage setting out to confirm, in numbers, the principle behind that sound — its first chapter is open.