>
>>
>> Linguolabial sounds are extremely rare, but not at all hard to
>> pronounce,
>> IMO. Just touch the tip of your tongue to your upper lip and release.
>> The
>> result sounds like a bizarre cross between /p/ and /t/ (which,
>> articulatorily speaking, it more-or-less is). If you're having trouble
>> pronouncing linguolabials because of the teeth, then you're probably not
>> opening your mouth wide enough.
>>
So the childhood expression of derision (a raspberry) is essentially an
unvoiced linguolabial trill?
Imperative