I personally find changes in sound and tone very interesting. Hopefully I'm not going to far with the information, but I thought I'd share a little background on some of the more common sound changes in Cantonese.
A note on the different examples you gave--
Many of the changes you are looking at are very similar to tone change rules, except these are sound change rules that are applied over a long period of time. Look at your first example:
參 cam1 / caam1 / sam1 / saam1:
-- 參加 caam1 gaa1 - to participate in
-- 入參 jap6 sam1 - ginseng
The initial "c" in jyutping corresponds to the symbol I have circled in both red and blue. It corresponds to the sound "ch" in English. Note that it is in the "palatal" column on the chart. A powerful force in sound change is called "palatalization" where sounds in nearby columns change into sounds in that column. The initial "s" in jyutping is also "s" in the IPA symbols (circled in red). You would expect it to become an "sh" sound, since that is the palatal closest to it, but because both sounds nearest on the chart do not exist in Cantonese (they're in yellow), so instead it moves to the "ch".
![Image](http://www.chinawestexchange.com/images/chart_cons_engl.jpg)
In cases like this, you could reconstruct the original sound through a number of different processes. But while there may be an original sound back in an older version of Cantonese, it no longer is the "default". In many cases the older version is preserved in a minority of sayings as the change sometimes leaves a sort of "fossil".
If you look at the other example of the "z/c" (I prefer j/ch) change, you'll see that these sounds are also very similar.
Hope that wasn't too boring.
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