Once, in my 30s, I woke up one morning and still had the sound of a giant surround choir in my head. I had dreamed up an exquisite harmony, sung by a very large choir in which I had heard every single voice.
Once in my 40ies, during a visit to Paris´ Notre Dame Cathedral, I was unexpectedly flooded with nearly unbearable physical bliss during an organ improvisation. My body was gripped by a kind of ever-increasing, self-reinforcing bliss-ecstasy, that sent wave after wave through my body, and I had to hide my streaming tears.
I never forgot it, and I had never again experienced music this way, until I attended my first Ayahuasca ceremony. Then, for example, the first sound of a large gong seemed to signify and to open up the entire universe. This was not bliss, but meaning and significance. On other occasions, I heard a harp as flooding my body-mind with celestial eternity.
The sense of hearing can do so much more than we normally experience.
How is this possible?
Music and psychedelics: reasons why music (usually) sounds so much better with psychedelics
Here, I want to largely confine myself to the effect psychedelics can have on this ability. In addition regarding dreams, I will add someone else´s dream music experience as an illustration.
I describe three theories in the context of the use of music in the new psychedelic therapies. Of course, this also is valid for the ceremonial use of music in, for example, Ayahuasca.
The three theories are:
Doors of perception: psychedelics open up the range of perceivable sensory stimuli and act as amplifier
Salience amplification: psychedelics create meaning
Symmetry amplification: psychedelics are "symmetry amplifiers", and symmetry is the basis for pleasure
Psychedelics and the "doors of perception"
For a start, psychedelics let one hear more (and smell more). There is an auditory amplification effect. This is well known. My own experience for hearing was the time, when someone violently and loudly shook a door in its angles, apparently trying to get in, and other experiences. In fact, when I went to the door, I noticed that it was just the wind gently pushing the door. Another example from my own experience is the sound of a drop of water falling 30 meters away in a large quiet hall.
A word of caution: exactly this amplification effect can spoil an entire Ayahuasca experience. The loudness and precision of the sounds may overwhelm the nervous system, so that the participant only wishes to flee the event. I know this through a close person who us auditorily very sensitive.
Psychedelics as meaning makers (the salience network)
Psychedelics increase the felt significance and meaning of perceptions by stimulating the salience network.
"The salience network is composed of interconnected brain regions, primarily the anterior cingulate cortex (ACC) and the insula. The ACC is involved in monitoring cognitive and emotional information, while the insula is associated with a wide range of functions, including emotion, self-awareness, and interoception (awareness of internal bodily states).
The salience network functions as a switchboard, constantly evaluating incoming sensory information and assigning significance to it. It helps determine what stimuli or experiences are most relevant or noteworthy at a given moment. This network plays a vital role in attention, decision-making, emotional regulation, and switching between different brain networks" (ChatGPT)
Research has shown that psychedelics affect the salience network (along with the default mode network) ((Pasquini et al., 2020).
This means, for example, that sound are loaded with much more meaning, significance and emotionality.. For example, my experience of the gong sound connected it with "a timeless time and the depth of the universe".
The salience effect is similar to what people may experience who suffer from schizophrenia. For example, a schizophrenic may experience the glance of a passer-by as a threat. This is one of the reasons why schizophrenia is a counter-indication for participation in psychedelic research or in well run ceremonies.
Psychedelics as symmetry amplifiers
This theory is a bit of an outlier. The postulate is that the phenomenology of symmetry is a cause for positive valence (valence is another word for feeling tone) and that psychedelics amplify the perception of symmetry.
This is definitely true for visual changes and appearances. Many of the pieces of psychedelic art show a strong degree of symmetry. I have a personal experience of seeing a "modified" face of my partner in a shared ceremony where her face had become completely symmetric and appeared as goddess. In fact, I later saw strong symmetries to Andrew Jones´ "Dragon Dharma"
Below you see an overview by research of the Qualia Research Institute (QRI). QRI investigate the properties of qualia. Qualia are what we experience as properties of objects, such as the smell of the rose.

The key proposition of this study is that psychedelics act as "neuroacoustic enhancers" (Gómez-Emilsson, 2020) through acting on symmetry properties akin to the perception of visual appearances as shown above.
Music in dreams
Concluding, and in addition to my own dream experience, I want to add an impressive dream recollection which is also descriptive of psychedelic experience of music.

So, dream music. I’ve had the pleasure or displeasure, you could say, of having had a lot of sleep paralysis and lucid dreams, and this effect is something you can experience in either sleep paralysis or lucid dreams. If you’ve had a lucid dream, where you were making music, or you heard, you’re hallucinating that there was a radio playing, you will notice that, “Oh my gosh, the music can be beautiful, like… incredible”. And this music, maybe you have heard it before, maybe not. Maybe your brain is generating it on the fly. But it has a quality to it that is extraordinarily hedonic and pleasant. And I remember studying this on myself over many lucid dreaming experiences. At first, I thought, “Oh my gosh, my brain is just unlocking this ability to create awesome harmonies and melodies”. But then I ended up realizing that even if I just make a kind of an “om”, this meditation sound, even though that sound is extremely simple, the quality of the sound in the lucid dream is profound. I mean, it’s almost kind of a surround sound, like 360 surround sound, and stereoscopic and full of reverb and richness. I would claim that it’s actually because, during a dream state, your brain is more resonant. You can kind of enter into these very, very resonant attractors, and it’s that quality that makes the music so compelling, not the melody. If you transcribe the melody, the melody may not be very significant. It was how it sounded that was so profound in the music in the dream (Gómez-Emilsson, 2020)
To Add
Hubermann and Carhart-Harris (2023), No studies made but could make the argument that it is music therapy
Hubermann and Carhart-Harris (2023), No studies made but could make the argument that it is music therapy: "Pychedelics without visions probably not effective"
Resources
Centauri, P. (2018, February 2). Riding the Soundcurrent: Steve Roach on Ambient Music, Creative Energy, and Introspection. Inside the Rift. Retrieved 18 September 2022, from https://www.insidetherift.net/interviews/2017/10/16/riding-the-soundcurrent-steve-roach-on-ambient-music-creative-energy-and-introspection
Gómez-Emilsson, A. (2020, December 17). The Symmetry Theory of Valence 2020 Overview. https://qri.org/blog/symmetry-theory-of-valence-2020#jhanas