Yeah I can also do this (sometimes), the experience is the same as yours: I can't quite emotionally resonate with the song as I would if I were hearing it IRL, but if I know the song quite well I can get all the details right.
It is particularly intriguing to be able to "sing" using other people's voices, since the lyrics of the song "feel" the same way as my inner voice, passing through (I assume) the brain's phonological loop.
Once I had this really weird experience, where in certain conditions, certain muscles would resonate exactly with the song playing in my brain (and not just the rythm, even minor details were somewhat transferred, as if my brain was redirecting raw PCM audio from my brain directly to the nerves); I was really excited about this, as there was potential for a direct non-invasive neural interface to my brain, capable of extracting original songs directly from my brain without any instruments; unfortunately I could not replicate this weird behaviour reliably, and I also felt a bit weird in my brain when trying to do so, so I just dropped the matter.
It is particularly intriguing to be able to "sing" using other people's voices, since the lyrics of the song "feel" the same way as my inner voice, passing through (I assume) the brain's phonological loop.
Once I had this really weird experience, where in certain conditions, certain muscles would resonate exactly with the song playing in my brain (and not just the rythm, even minor details were somewhat transferred, as if my brain was redirecting raw PCM audio from my brain directly to the nerves); I was really excited about this, as there was potential for a direct non-invasive neural interface to my brain, capable of extracting original songs directly from my brain without any instruments; unfortunately I could not replicate this weird behaviour reliably, and I also felt a bit weird in my brain when trying to do so, so I just dropped the matter.