Is the "j" in "jsem", "jsi", etc. pronounced?
The recordings make it sound like "jsem" is pronounced like "sem" without the "j" sound. Is this the case? Is this true only for conjugations of the verb "to be" or for other words as well?
You won't make a mistake if you pronounce it every time. This heavily depends on the local accents, people from Prague mostly don't pronounce it at all, so "jsme", "jste", "jsi" becomes "sme", "ste", "si". It applies to other words as well, "jméno" becomes "méno", "jmenuji se" just "menuji se", and "jdu" turns into "du". This is, however, only spoken, informal language. And people from northern Moravia would most likely pronounce the "j" in each of these words.
So don't worry about it and pronounce it. Just don't be surprised when listening to Czech people speaking ;).
In my experience in the Czech Republic, the j is not pronounced in the verb "to be", i.e. jsem, jsi, jste, etc. But it is pronounced when preceding other words, like "jméno". (name)
I think its more of an accent type thing in standard Czech like I hear j at the beginning of the word pronounced far less frequently depending on the part of the country you are in.
You should pronounce (or make the effort to pronounce) the J when the word is stressed. Even in words like jsem, jsi, jsme, jste. - eg. Jsi tady? Jsem. (For learners it might still be difficult to catch though and not to blame you, some people are lazy and use colloquial Czech, which then makes it impossible to hear. :-) ) Also, you should pronounce the "j" in all the negatives - nejsem, nejsi, nejsme, nejste, nejsou.
I never said you shouldn't say it I just said in my experience I hear it more like and accent where it is more or less pronounced depending on where in the country you are
Yeah, sorry, I should have posted it as a new comment, not a reaction. I agree with what you said. :-)
It should be pronouced when 'být' and its conjugations are used in the sense 'to exist' - 'Já jsem žena.' - I am a woman. It's not mandatory, the 'j' is pronouced mainly to sound more refined and polite. When 'být' isn't used that way, it shouldn't be pronouced.