Thanks, frank, for the excellent topic.
With respect to people not speaking a foreign language with perfect pitch and intonation, your are quite right. If a foreign language is acquired after the age of about seven-years-old, the speaker (except in very rare cases) never will be able to duplicate the exact timbre, pitch, intonation, etc. of the native speakers. Is this a deficiency? I am of the opinion that there is no "perfect" way of speaking a language, given the spontaneous development of pidgins (a topic that I find fascinating because of the broad implications of the relationship between inherent? ability based on physiology and environmental influences). Of course, beginners and woefully untalented speakers never are the originators of any pidgin, except, perhaps, that which has become the language of Americans abroad, inciting vehement disdain among Parisian cafe waiters.
I am trilingual in English, French, and Italian, and definitely have noticed that my voice changes quite dramatically from one language to the other. My multilingual acquaintances also have noticed this, and even have said that I become another person when I speak one or another of the tongues. I believe that this ability was birthed by the fact that I am a native speaker of each language.
The study of phonology is wildly dense, and draws upon so many related disciplines in the linguistic, natural, and social sciences that it is difficult to synthesize a coherent answer to your question. To boot, the unbelievably vast subject of semiotics increasingly is considered as an important, related (fuzzy?) course of inquiry as far as the effect of meaning on phonology and vice-versa. At any rate, the subject is enormously gratifying, as are, I think, areas of study where workers have realized the value of cooperation between the natural and social science camps. I’m afraid that there is no short answer to your query, but I believe that you will enjoy looking into it.
A terrific starting point for your research:
http://www.universalteacher.org.uk/lang/phonology.htm#what
To spark your interest, here are some of the topics treated on the above page:
-Physics and physiology
-Phonology, phonemes, and phonetics
-The sounds of English
-Diphthongs
-Suprasegmentals
-Accent and social class
-Language acquisition
-Language change
-Different ways of representing sound
References:
timbre
n.
1. The combination of qualities of a sound that distinguishes it from other sounds of the same pitch and volume.
[French, from Old French, drum, clapperless bell, probably from Medieval Greek timbanon, from Greek tumpanon, kettledrum.]
2. The quality given to a sound by its overtones: the resonance by which the ear recognizes and identifies a voiced speech sound : the quality of tone distinctive of a particular singing voice or musical instrument
3. (music) the distinctive property of a complex sound (a voice or noise or musical sound); "the timbre of her soprano was rich and lovely"; "the muffled tones of the broken bell summoned them to meet".
Author’s Note: I find the etymology fascinating, especially because of the word drum, which connotes vibration.
prosody
n.
1. The study of the metrical structure of verse. A particular system of versification.
[Middle English prosodie, from Latin prosdia, accent, from Greek prosidi, song sung to music, accent : pros-, pros- + id, song; see ode.]
2. n 1: the patterns of stress and intonation in a language [syn: inflection] 2: (prosody) a system of versification [syn: poetic rhythm, rhythmic pattern] 3: the study of poetic meter and the art of versification [syn: metrics]
Author’s Note: I strongly believe that music will provide many answers to this question of accent.
inflection
n.
1. The act of inflecting or the state of being inflected. Alteration in pitch or tone of the voice.
... A turning or bending away from a course or position of alignment.
modulation
n.
1. The act or process of modulating. The state of being modulated.
2. (Music) A passing or transition from one key or tonality to another.
3. A change in stress, pitch, loudness, or tone of the voice; an inflection of the voice. An instance of such a change or an inflection.
4. The harmonious use of language, as in poetry or prose.
5. (Electronics) The variation of a property of an electromagnetic wave or signal, such as its amplitude, frequency, or phase.
VB