Practices using sustained sound appear in temples, retreats and wellness settings, framed in various traditions as working on energy. Several of their effects can be described more precisely.
Sustained tone regulates breathing
Producing a long vocal sound requires a slow controlled exhalation, since the note ends when the breath does.
Group chanting therefore imposes a breathing pattern with extended out-breaths on everyone participating, whether or not anyone is thinking about breath.
Slow breathing of this kind is associated with measurable changes in heart rate patterns, which accounts for part of what participants describe without requiring any further explanation.
Vibration is physically present
Voiced sound produces vibration in the chest, throat and skull that the person producing it can feel directly.
Low sustained tones from instruments are also felt as well as heard when the source is close, since the body transmits and responds to pressure waves.
This is a real physical phenomenon and it is what practitioners are pointing at, though it does not by itself support claims about tuning organs or realigning fields.
Sound occupies the channel that inner speech uses
Continuous vocal or auditory activity competes with the internal verbal stream, which is why chanting is often described as quieting thought.
The effect is attentional and immediate, and it is one reason recitation practices are found in traditions with no shared theory of sound.
It also explains why practitioners often find vocal practice easier than silent sitting at the start, since the task is more obviously defined.
Group sound produces synchrony
People chanting together fall into a common rhythm and a common breathing pattern, and researchers have documented physiological synchronisation in group singing.
The social effects of doing something demanding in unison are substantial and well described across many activities.
Attributing the resulting sense of connection specifically to sound therefore understates how much of it comes from coordinated collective action.
Claims should be separated by type
Statements about relaxation, attention and mood are the most tractable of the claims made, since they concern reported experience and can be investigated directly.
Statements about specific frequencies affecting particular organs or emotional states are not established, and the frequency figures circulating in popular material have no consistent basis and vary between sources that cite each other.
Separating these two kinds of claim makes the practice easier to discuss honestly and easier to defend where it does work. Sound sessions are not a treatment and should not replace medical care for any condition.