pronunciation - Utterance initial [ɾ]

According to The sounds of Japanese (Vance 2008):

When /ɾ/ is the first phoneme in an utterance, the tip of the tongue is already resting lightly on the alveolar ridge, and /ɾ/ is produced by rapidly releasing this contact. Strictly speaking this utterance-initial allophone isn't a tap.

1. 
   
   

   Can anyone elaborate on this utterance initial [ɾ] and its allophonic derivation, perhaps giving a reference for further reading? If it isn't a tap, then what is it? It sounds like it might be a voiced plosive, but it doesn't feel similar to either alveolar plosives [t, d]. It certainly sounds like there is an r-quality to it, but I wouldn't know how a plosive might acquire an r-quality.

   
   


2. 
   

   Are you actually realizing, and furthermore aware of, an allophonic variant of [ɾ] (specifically the apparent utterance-initial allophone)?

   
   

Answer

Wikipedia seems to say it is alveolar lateral flap, as opposed to the otherwise alveolar (central) flap. If you are serious, maybe you might want to try the article cited there. Trying this with myself, I seem to get the difference. I seem to be able to freely alternate an initial alveolar lateral flap with a centered one, but not a non-initial alveolar flap with a lateral one.