I read MCTB less than two months ago, and decided to try Concentration meditation (I've decided not to start Insight meditation yet). I've been tentatively labeling various experiences as being various jhana's as I went. Tonight I experienced something which seems like it might have been 4th or 4th followed by 5th jhana, so I feel I should get some outside opinions. I'm not going to bother calling my labels tentative in the rest of the post, but I'm open to being convinced they are incorrect.
My practice has been very sporadic, basically whenever I happen to feel like meditating. I haven't used the breath as an object very often, as it felt difficult to me. My initial progress was using my body as the object, often focusing on the sensations of my muscles relaxing. I experiment occasionally, but if I have trouble concentrating I move on. I found that music seems to be a productive object for me to meditate on as well.
My concentration has improved over time, but it doesn't seem especially important that I try my utmost to only be aware of the object. A casual awareness is usually enough to at least maintain my position. Being more immersed in the object does seem important to move forward, though.
When I first sit, there is a period of physically and mentally settling down. Its partly muscles relaxing, but there is also a mental/perceptual shift, my body becoming slightly fuzzier or more distant. When using the body as an object sometimes I notice feeling like there is a shell over my body. Perhaps a kinesthetic mental image of the body. I've been calling this First Jhana.
The Second Jhana often seems to contain funny internal sensations, prickly feelings and that sort of thing. I'd notice my skin being tugged outward, and then notice that my muscles were unconciously tensing, so I'd loosen them, and shortly afterward feel more internal sensations. The exact sensations seemed to change often. As I mentioned before, there would often be muscle spasms, and physical twitching. I remember once feeling an internal quake somewhere along my spine, and shaking briefly. Entering the state was often accompanied by a pleasant wave, and a shift from holding the object very tightly to more loosely. Most of the time the shift from the first, to the second was automatic, though once I triggered it intentionally by purposefully increasing the perception of a shell, and then releasing it. One day, I noticed after sex, that there seem to be some common ground between post-orgasm and this state, though the overall quality of the experience seemed pretty different, at least due to context.
The shift into Third Jhana came the first time I used music as my object for meditation. This was also my longest sit so far, about an hour and twenty minutes long. I was in Second Jhana for most of that, and this is when I noticed that the various internal sensations seemed to cycle. They did get very tiresome, and then there was a sudden shift. At first it seemed like they were gone completely, but after a bit I realized they were present but much quieter. There was a definite sense of equanamity. I also noticed that it no longer seemed like I was pushing my attention into the music, instead it was more like I was leaning back and letting it come to me. I'm not very familiar with this state, since I haven't meditated as often since first reaching it. I think I've entered it one other time since then (not counting tonight, which I'll recount below), though the transition was not as pronounced, and the sense of equanamity wasn't as amazing. This was a bit dissapointing, and contributed to the fact that I didn't meditate very much, or intensely for a while.
Tonight I had my second successful session using music as an object. I was listening to Pandora, so I'm sure it was less than an hour, probably about 40 minutes. I'm not entirely sure about the order of most of these events. I remember settling in. At some point I switched from pushing into the music, to letting the music come to me. (this was a decision, I think). At some point I noticed a white dot out of the corner of my eye. It went away, and I noticed some other white dot. At first I was trying to ignore it, but then I decided it was fine, and this was followed by a larger blob of white crossing the center of my vision. At some point there was a shift from the music being the thing, to the whole stream of experience. The back of the eyelids, and the feelings in my body. I had noticed them before, but this was different. This wasn't a decision, though shortly after I decided that I should accept it. A little later I felt some vertigo, sort of like I was tumbling forward. It felt like my head was rotating forward into my chest, and my stomach was rotating upwards. This went on for a couple seconds, and then I was very small and very large. Its hard to describe, I think the sensation of largeness was because my left thigh was aching, and it felt far down below, but I'm used to thinking of my head as the center of my mind, so I subconciously calculated as being very large. But I also felt like a single point, floating in space.
I'm not sure what that was, but it seems like it might have been 4th followed by 5th jhana. On the other hand, I'm pretty unfamiliar with 3rd Jhana still, so maybe it was 3rd to 4th. Or just 3rd. Or crud, I'm a newb, maybe all of this is totally wrong, you tell me

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