Why has music a healing effect?
First of all it is because of the meter. The meter has in it the primal feeling for humans. When you look at baby's they already do everything in a certain rhythm or meter; they are rocked by the mother in a fast meter, but they also suck the thumb in this meter. Even when they take their first steps it is in the same meter. But it starts even earlier. When the baby is still in the stomach of the mother there is already a fast meter they listen to; the heartbeat of the mother. This in combination of the rocking in the stomach because of the water and listening to the voice of the mother; we are born with music. So you could probably understand that music has an healing effect, because it calms us. And the reason that is calms us is because it brings us back to the meditating primal feeling that our body remembers of being a baby.
but not there is more to it; because music is not only existing of meter of rhythm. We can also look at melody and harmony. Music in it has the power of nature. Think about the whistling of birds or a rippling water brook. We hear music now as music, but the 'rules' and techniques are all natural. That is why we like consonants and dislike dissonant tones; those tones aren't usually to be found in nature. Like the different between larger objects and smaller objects; they produce a lower and higher sound. We would find larger objects more intimidating, so a lower sound would nerve us more than a light high pitched sound. Melody is often mirrored with speech; we use the same technique in talking to make feelings clear than we do in music. Sad music often has smaller intervals, just like a sad person is more likely to talk monotone.
Harmony is also naturalistic; each instrument vibrates when producing sound. This vibration often gives one tone, but it has more tones in it; the same as often found in chords. You'll call this overtones or harmonic sequence. These tones naturally found in one chord are the 3th and 5th;
So music is calming because it brings us back to nature, but also to our baby time without problems to worry about. That is the reason why we dance on rhythm and not on melody; we rock ourselves around to relax and enjoy the music. Melody tells the story of the song, because it has in it the language of speech and nature. We understand it because it merged with natural features such as the wind going through the trees. Harmony then can be satisfying because we can hear the tones of one tone in completing form.
Yours Sincerely @inMusicalTerms
P.s.: check out my collaboration with other steemians in which I sing: https://steemit.com/dsound/@davidfar/20180225t120107080z-a-strange-day-original-music-a-live-steemian-band-from-around-the-world