The album's coda is in fact what the rest of the album's cuts have been inaccurately accused of being: a pretty (or pretty odd) musical snippet that doesn't make a whole lot of sense.
Fair enough. The melody line is introducted by whistling over a dum, dum, dum doo-wop bass. After which the vocals take over with some Smiley style intrumental backing.
Lyrics: "Whistle in. Remember the day, day. Remember the night, night. All night long." Seven times in about a minute. Fade to out.
What does it mean? Whistle In may be an allusion to a 1960s progression. Civil Rights: Sit In. Viet Nam War: Teach In. Hippies: Be In. The rest: perhaps side two does contain a sequence. Boy gets vibrations from girl, boy wants girl, girl leaves and comes back. Or something like that.
Or maybe it doesn't mean anything and isn't supposed to and doesn't need to. If side two works, then "Wonderful" was the conclusion and this is just a bit of wrapping things up. And we're done.