A correspondent writes to ask if singing is ever used in speech. She isn't thinking of intonation, sometimes described in a metaphorical way as the musical property of speech - ‘metaphorical’, of course, because our voices don't need to be tuned to concert pitch before we begin a conversation. She has in mind something rather less obvious - musical quotations or catch-phrases, where a musical extract is given a generalized linguistic interpretation.
Yes, there are instances. I've heard people sometimes say Hallejuah! when a satisfactory outcome has been achieved, but instead of saying it they sing it as the opening bars of the chorus from Handel's Messiah. I can't think of many like that. Rather more common is the vocal rendition of orchestral fragments. A contemporary example is the theme from Jaws. The jocular expression of an approaching dangerous social situation is often conveyed by people sounding out its ominous low-pitched glissando quavers. It forms part of a dialogue that is otherwise speech, and it's meant to be judged by the same standards. Nobody thinks of it as an attempt to artistically render the original musical score.
I've collected several examples of this kind in conversational settings: the theme from the Twilight Zone, Dr Who, Dragnet, the shower-room scene in Psycho, Laurel and Hardy’s clumsy walk music, the riff in Close Encounters of the Third Kind, and the opening motif of Beethoven’s Fifth Symphony. The extract is usually highly stereotyped and brief. It may be just a couple of notes. Someone who arrives in a room with something special to show may accompany it with ‘Ta-raa’, or the fanfare from a racecourse. I've heard people use the whistled motif from Clint Eastwood’s Spaghetti Western films and the chase music from a Keystone Kops film. Devotees of The Prisoner cult TV series (the original one, not the Hollywood remake) introduce its brief musical motifs into their speech to the point of boredom. TV ads can prompt the use of a tune. I'd be interested to hear of other cases.
What is linguistically interesting is that some of these excerpts make sense even if the participants have never encountered (or have forgotten) the original version. The Jaws theme, for example, has taken on a life of its own - a musical idiom expressing mock danger. In such cases, the semantic interpretation is clear. On the other hand, in cases such as the Dr Who theme, the function seems to be pragmatic rather than semantic - to build rapport among people who have shared a cultural experience. Some of the examples may be very transient, therefore, and (as in the case of TV ads) may not make sense outside of the regional setting in which they were first heard.
Phoneticians have problems with these things. They aren't easy to transcribe, not least because they use an absolute musical scale, whereas speech uses a relativistic scale. It doesn't make sense to think of people as speaking 'out of tune' (though some prosodic disorders in speech pathology might aptly be described in that way). Try transcribing the theme from Jaws, and you'll see the problem straight away.