No answers about "why" or "how come", but some examples from Chinese
languages of varieties which exhibit a particular phenomenon. (Based
on Wikipedia information.)

On Tue, Jul 8, 2008 at 18:11, Eldin Raigmore <[log in to unmask]> wrote:
> How do languages come to have more than one level tone?  And which ones
> do?

For example, Moiyen Hakka (/44/, /11/); Standard Cantonese (/55/~/53/,
/33/, /21/~/11/, /22/); Toishanese (/55/, /33/, /22/~/11/); Quanzhou
Minnan (/55/, /33/, /22/).

> How do languages come to have more than one rising tone?  And which ones
> do?

For example, Standard Cantonese (/35/, /13/); Tianshui Mandarin (/13/, /24/).

> How do languages come to have more than one falling tone?  And which ones
> do?

For example, Moiyen Hakka (/31/, /53/); Tianjin Mandarin as well as
Amoy and Zhangzhou Minnan (/21/, /53/); Zhengzhou Mandarin (/42/,
/53/); Toishanese (/31/, /21/).

> If three pitches (say High, Medium, and Low) are involved in the tone-system,
> there are three possible rises; LM, MH, and LH.  Do any natlangs have all
> three? If so, which natlangs?  If not, do any have both LM and LH? Which? Do
> any have both MH and LH? Which? Do any have both LM and MH? Which?

Standard Cantonese, for example, has LM and MH (/13/, /35/).

> Likewise for falls:  Which, if any natlangs, have both HM and ML? both HM and
> HL? both ML and HL? Which, if any, have all three?

Toishanese apparently has /31/ and /21/, which seem to terminate at
the same point but originate at different points -- ML and LL,
perhaps?

Shijiazhung, Kunming, and Lanzhou Mandarin have /53/ and /31/ (though
as realisations of different tones), i.e. HM and ML.

> Do any natlangs have more than one rise and also more than one fall?

Standard Cantonese (two rises and two falls, though both falling tones
have level allotones).

> Why would a tonal language with three or more pitches in its tone system, and
> with both level tones and glide tones (rises and falls), need any contour tones?
> Are there any such natlangs?  Which ones, and/or how many?  And what are
> their tone systems like?

Standard Mandarin has one level tone /55/, one rising tone /35/, one
falling tone /51/, and one dipping tone /214/.

> Why would a tonal language with both level tones and glide tones need more
> than three pitches in its tone system?
> Are there any such natlangs?  Which ones, and/or how many?  And what are
> their tone systems like?

Standard Cantonese seems to have four significant pitches -- it has
/55/~/53/, /35/, /33/, /21/~/11/, /13/, and /22/, i.e. all of /1 2 3
5/ are used.

Similarly with Toishanese, which also uses /1 2 3 5/ in its tones:
/55/, /33/, /22/~/11/, /31/, and /21/.

Cheers,
-- 
Philip Newton <[log in to unmask]>