I'm sure it's the same. Letting oneself slide into heavy Fi mode. Not lucid dreaming but something similar - very rich and satisfying.
I tend to see Fi as being strongly attached to emotional and memory associations. The following post is highly speculative (i.e. my own personal theorizing), but it might help others get some insight into how Fi works or come up with their own theories about Fi. But take it with a grain of salt.
Just about everyone has experienced flashes of old memories associated with a certain smell or flavor. Let's say I lived at the beach in my childhood but later moved to the mountains. When I finally return to the beach decades later for the first time since childhood, my first exposure to the odor of the salt air will almost certainly bring back a flood of long-forgotten childhood memories.
Researchers say that our sense of smell (and hence, our sense of taste with it) has the strongest power to bring back old memories because the wiring for smell is buried deepest and connects most directly to the core of the brain. Evolutionarily speaking, smell was the strongest and most accurate of the 5 senses for interacting with the world in most early mammals. Thus, the scent of a forgotten flower, the taste of a forgotten meal from another part of our life, the strong smell of hospital antiseptic or diesel fumes from heavy equipment, etc., has the power to bring old memories and experiences back vividly. Proust's classic novel "Remembrance of Things Past" begins with the phenomenon of childhood memories brought to the surface when the narrator has a cup of tea and a bite of a madeleine pastry while visiting his grandmother.
Other senses (touch, hearing, and sight) are much weaker in terms of memory associations. They traditionally don't bring back full-fledged memories at first. They're more likely to bring back old emotions initially. That's because memories are best retained when they are tied to an emotion, and the emotion tends to come back first (vaguely and confusedly) when old associations are made through the weaker senses.
Thus, let's say I'm walking around an empty museum and I listen to the echoing clatter of my steps, and I get a sense that I've heard that sound before sometime in the past. If I keep listening, I may even get a sense of foreboding and dreariness from the sound (i.e., emotional content appears). If I want to pursue the sensation further, I may keep walking and listening, speeding up and slowing down my steps, repeating the sounds and rhythm that seem to have the most "resonance," until I suddenly remember walking down an empty hospital corridor as a child, ill with some sickness and not really paying attention to my surroundings, but also vaguely dreading the unknown treatment that awaits me at the end of the corridor.
IOW, I start with a vague sense of familiarity and then build to an emotion and then to a memory.
I can't speak for everyone, but it seems to me that a lot of INFPs get entertainment from pursuing these kinds of old associations, emotions, and memories. From this, you get the stereotypes of infantile-acting INFPs trading in random scraps of old childhood memories, free associating with giddy whimsical jokes (a good way to mine the brain for random associations), and even re-reading children's books from their own childhood in the hopes of dredging up some old memories. Some INFPs assume that these old scraps of memories and associations must have had a certain mystical power (in the sense of a personal revelation) if they were able to return from nothingness after many decades, and so a minority of INFPs make a fetish out of chasing after childish whims and insisting that their long-lost childhood represents some kind of personal golden age.
In a way there is a kind of hypochondria to it, in the sense of a hypochondriac seizing on and mapping out every little bodily ache and twinge in both dread and hope of finding something seriously wrong.
On the other hand, using associations and memories is a fast and efficient way of analyzing and making decisions. It's how people get a "gut feeling" about something. If a certain experience has repeatedly left you with a bad feeling over time, then to a certain extent one can use that "bad feeling" as quick input for judging how best to react to a situation as it arises.
But obviously INFPs should also realize the fallibility of "gut feelings," especially ones that go all the way back to childhood. The Ne of INFPs should be used to sort and analyze memory associations and compare them to the objective measures of the outside world; INFPs shouldn't uncritically accept childish fears and enthusiasms about external events to determine their personal values.
Thinkers usually at least register the existence of strong emotions (disgust, hate, love) and probably register the rare flood of memories associated with a certain taste or smell. But they will probably dismiss outright the weaker emotional associations attached to touch, hearing, and sight. Fi people can dismiss them just as effectively. An Fi person may simply be too busy or occupied to pursue a weak emotional association that pops up while walking down the street; or, having pursued the association, he may determine that a childish memory or emotion that was dredged up is too old and simplistic to be of any use and dismiss the whole thing.
But much as Thinkers like to analyze for the sake of analyzing, Fi people may dabble in old emotional associations for fun. Particularly ancient and vague emotional cues can be fun to unravel as mental exercise; and for the connoisseur, old emotions can come in a variety of "flavors." The recovery of an old childhood memory can yield a sense of surprise and nostalgia.
Some Fi people may not bother to chase down old memories and may simply enjoy the interplay of emotions at the back of their consciousness when experiencing a particularly rich environment (one that has a lot of sensual cues to trigger associations). For many Fis, the emotions are the more interesting part; by comparison, the memories may involve work and may be much less interesting. When Park describes listening to music, I think she is describing an experience of enjoying the emotions triggered by the music without going into the past to determine what specific past experiences linked those emotions to those tones or percussion or style of music. (That's a perfectly acceptable use of Fi.)
Furthermore, as they get adept at playing with emotional cues, Fi people can play around with the external emotional cues of others (body language, vocal cues, choices of words) or even extrapolate themselves into the emotional crises of others in order to see how they themselves would handle the situation.
Also, becoming adept with emotions obviously gives Feelers an edge in communication skills. By ignoring emotional cues, Thinkers clearly put themselves at a disadvantage in that area.
The danger for Fi people, of course, is that they will make a fetish of their internal emotional associations and never learn to sort and analyze their "gut feelings" in terms of objective value. They become solipsist and self-involved. They may disregard emotional cues from others as unimportant compared to their own personal emotional "revelations," and become selfish and self-contained.
Fe people (Extroverted Feelers) are more attuned to emotional cues from others and presumably don't put as much stock in emotional associations generated from within. The danger for them is that they will become masterful at interpreting and manipulating the emotions of others but never really look inside for a personal experience of how those emotions "feel" to the recipient. Emotions will simply be a tool for organizing the people around them, without much consideration for how the people are actually feeling those emotions.
Sensor Fis (ISFPs) seem to deal in personal associations that arise from sensation. When they engage in art, for example, the art seems to be about putting together different combinations of sights and tactile sensations in order to try to approximate some personal internal ideal; presumably the ideal is derived from some old experience or personal association and they are trying to externalize it in an idealized form. They often seem unable to describe the ideal or where it came from. They repeat an artistic process many times, apparently knowing only for a certainty that the results are closer or further from their ideal even though they are unable to describe the ideal or its meaning. (Note the similarity of this process to my earlier example of walking up and down a museum hallway trying to match the sound of my footfalls to an unknown memory.)
Intuitive Fis (INFPs) deal in personal emotional associations. The old memories that are linked to the emotions, in fact, seem to be less important than the emotions themselves. The memories justify the emotions, but it's the emotions (the pain, the fear, the anger, the love, the sense of belonging) that really seem to be important to INFPs. INFPs probably can't enunciate what they hope to achieve with these emotional experiences; with no justification for their quest, they can take on the appearance and even the habits of emotional junkies. But given the nature of Intuition, I suspect INFPs would ideally like to understand where their fears and emotions first arose and then weave these emotional scraps and understandings into a kind of childhood emotional safety blanket. INFPs often hearken back to an idealized infancy of peace, tranquility and acceptance: a kind of pre-individuation personal Garden of Eden. INFPs often talk of a feeling of "innocence lost" and a quest to return to simpler times and merge themselves back into a larger, more comprehensive consciousness. Emotional associations seem to be the path for them.
And from this last step, you get the INFP fascination with "human spirit." INFPs may ask what, in fact, constitutes humanity itself if not human emotions, and then chase emotions to their very roots and project how they could be formulated differently depending on environment and personal experience.
But again, the usual cautions apply. Without proper use of Ne to filter the emotional cues and compare them to outside objective measures, it's all just an exercise in infantile solipsism. It's just navel-gazing. Frankly, only a few INFPs ever really manage to get it right and extrapolate properly from the personal to the universal.
