I won't try to explain what Solfeggio frequencies are - I'll leave that to the Solfeggio Ascension Frequencies site.
Listening to the tones took some time getting used to - the sounds are not the most relaxing, but after the second day, I became used to it.
The most noticeable thing I experienced was a slight pain in the area of my belly chakra. It was just annoying, nothing that bad, and went away relatively quickly after listening to the tones (a listening lasts for about 10 minutes). I felt my hand chakras, third eye, and crown chakra tingle at times, but it was nothing unsual to me having worked with Reiki, meditation, and other spiritual practices.
The second day was more laid back than the first. I felt a bit of pain in my belly chakra, but it was less than the first day. I was actually surprised this time, though, as I felt pretty relaxed by the end of it.
If I get any interesting experiences while listening, I will definitely share them here.