My understanding is that if only the citation tones are written, Cantonese speakers would be able to fill in the tone changes themselves based on context and experience.
I agree. Cantonese speakers should be able to fill in the tone changes based on context and habitual usages, or choose to use the citation tones based on personal preference.
Of course, in textbooks and dictionaries, these tone changes would be indicated so that they may be learned in the first place.
Textbooks would readily indicate any tone changes for certain terms to cater to the learners’ need.
Dictionaries, on the other hand, would refrain from indicating a tone change for a character unless that change is extremely popular for most cases. Take the common character 門 as an example. 門 uses the citation tone 4 in 大門, 正門, 鐵門, and 專門 (when it means “technical” ), but also uses the changed tone 2 in 前門, 後門, 橫門, 熱門, 冷門, 偏門 and 專門 (when it means "specially" ). When I look up 廣州話正音字典, 廣州話方言詞典, 粵語拼音字表, CUHK site and Education Bureau site, none of them gives a tone-change reading. Only 廣州話普通話詞典 gives both mun4 and mun2.
However, I don't believe that it's necessary to account for them when typing Cantonese phonetically into a computer or mobile device (many modern IMEs do not even account for any tones).
Regarding those characters (e.g. 門) that have unpredictable and optional tone changes based on phonetical grounds, I share your view that it is not necessary to account for them.
But for those tone changes based on, for instance, semantical grounds, I think it is necessary to indicate both the citation and changed tones. 糖 is a typical example where the citation tone 4 is applied to its original meaning “sugar” while the changed tone 2 is applied to the extended meaning “candy”. In that case, we may argue that tone 2 is actually a separate tone rather than a changed tone.
… a syllable's change to tone 2 seems to happen when its character constitutes a part of a compound.
Most tone changes are brought about by the effects of adjacent tones of a compound. In other words, the changes are most probably based on phonetical (e.g. 前門 with two adjacent tone 4) and morphological (e.g. tone 4 for first syllable of kinship terms) grounds.
However, for tone changes based on semantical and syntactical grounds, they are applicable even to single characters. For example, 糖 has tong4 (sugar) vs tong2 (candy); 袋 has doi6 (to pocket) vs doi2 (a pocket). Such changes involve those characters that do not constitute a part of a compound.
I agree. Cantonese speakers should be able to fill in the tone changes based on context and habitual usages, or choose to use the citation tones based on personal preference.
Of course, in textbooks and dictionaries, these tone changes would be indicated so that they may be learned in the first place.
Textbooks would readily indicate any tone changes for certain terms to cater to the learners’ need.
Dictionaries, on the other hand, would refrain from indicating a tone change for a character unless that change is extremely popular for most cases. Take the common character 門 as an example. 門 uses the citation tone 4 in 大門, 正門, 鐵門, and 專門 (when it means “technical” ), but also uses the changed tone 2 in 前門, 後門, 橫門, 熱門, 冷門, 偏門 and 專門 (when it means "specially" ). When I look up 廣州話正音字典, 廣州話方言詞典, 粵語拼音字表, CUHK site and Education Bureau site, none of them gives a tone-change reading. Only 廣州話普通話詞典 gives both mun4 and mun2.
However, I don't believe that it's necessary to account for them when typing Cantonese phonetically into a computer or mobile device (many modern IMEs do not even account for any tones).
Regarding those characters (e.g. 門) that have unpredictable and optional tone changes based on phonetical grounds, I share your view that it is not necessary to account for them.
But for those tone changes based on, for instance, semantical grounds, I think it is necessary to indicate both the citation and changed tones. 糖 is a typical example where the citation tone 4 is applied to its original meaning “sugar” while the changed tone 2 is applied to the extended meaning “candy”. In that case, we may argue that tone 2 is actually a separate tone rather than a changed tone.
… a syllable's change to tone 2 seems to happen when its character constitutes a part of a compound.
Most tone changes are brought about by the effects of adjacent tones of a compound. In other words, the changes are most probably based on phonetical (e.g. 前門 with two adjacent tone 4) and morphological (e.g. tone 4 for first syllable of kinship terms) grounds.
However, for tone changes based on semantical and syntactical grounds, they are applicable even to single characters. For example, 糖 has tong4 (sugar) vs tong2 (candy); 袋 has doi6 (to pocket) vs doi2 (a pocket). Such changes involve those characters that do not constitute a part of a compound.