When speaking French, not all words are pronounced separately: words are grouped and linked together. A group of words is said the same way a very long word would be: this is called the rhythmic group. The rhythmic group is a group of words pronounced in a single breath. A rhythmic group often corresponds to an idea. Example:
"toutes les occasions sont propices" = dee-dee-dee-dee-dee-dee-dee-dee-dum (= an 8-syllable word).
It does not usually exceed seven syllables. It is only the word at the end of the rhythmic group which is a stressed syllable. These are referred to as noticeable sentence stresses. That syllable lasts a bit longer. If the end of the group does not coincide with the end of the sentence, the voice rises on the last syllable of the group, to indicate that we are not finished speaking. Examples:
"une bière ↑, ou un cognac ↓"
"il est même inconcevable ↑"
"toutes les occasions sont propices ↑" à manger et à boire.
"de bavarder avec quelqu'un ↑" A word does not have a stressed syllable when it does not come at the end of a rhythmic group. Example:
"occasions" in "toutes les occasions sont propices" At the end of a sentence the voice falls. Example:
"à manger ou à boire ↓"
Note that in order to show the difference in length, the last syllable is represented as "dum," while the other syllables are "dee," usually perceived as shorter sounds.