Ogni frase deve essere inserito in un contesto, nella frase precedente sicuramente c'è il soggetto (io oppure tu) e, di conseguenza, sappiamo chi sta parlando. Es: Mi stavo chiedendo (io): e se parlassi un po' di meno? Stai dicendo un sacco di fesserie (tu): e se parlassi un po' di meno? Nel caso non ci sia un soggetto chiaramente espresso e ci sia il rischio di ambiguità, io o tu vanno inseriti prima, o talvolta dopo, del congiuntivo. Ad esempio, un libro narra che, a teatro, uno spettatore disturba, il protagonista lo riprende e nasce un fastidioso battibecco. Leggiamo: e se parlassi un po' di meno? (può essere il protagonista del libro che lo sta pensando tra sé rivolto a se stesso, oppure lo sta dicendo al disturbatore). Nel primo caso diremo: e se IO parlassi un po' di meno? nel secondo: e se TU parlassi un po' di meno? al che, il disturbatore potrebbe rispondere. E se parlassi TU un po' di meno?
Spero sia chiaro.
It's absolutely impossible to know who the subject is. It may be I or you. But it's also absurd to find a clause without a context. Were I to find a piece of paper on which someone wrote: ...spoke to the Queen! Could you tell me who spoke? And in this case we have not only I and you as unknown subjects, but also he, she,we you and they.
Thank you .... that's what I thought but I wasn't sure if there might be some rule about what you could or should assume if you had no other information. At least I now know that it's not me being particularly dense. You have been a great help to me as usual my friend :-))
In the past subjunctive the two verb forms are all the same: che io parlassi, che tu parlassi. In the present subjunctive it's even worse, the singular forms are all the same. To be unambiguous in Italian you'd have to use the personal pronouns (which is something you always do in English but rarely in Italian).
An important point of grammar: the two sentences have different subjects not different objects.
It's important because of the difference between nomination (subject) case and objective case in English (the only two cases in most English sentences and phrases):
Subject (Nominative case): He
Object (Objective case): Him
That's a different subject, simply a choice Duo made. Duo chose a verb parlassi with two possible subjects: I/you. With parlasse, there are three possible subjects: He/She/Formal You (Lei). "It" is not a possible subject because inanimate objects don't speak (expect perhaps in poetry.)
The conjugation here is:
Obviously context is everything here to differentiate "I speak" from "you speak."
IMPERFETTO che io palassi che tu palassi http://www.italian-verbs.com/italian-verbs/conjugation.php?parola=Palare+
To the point about English subjunctive, possibly a better translation using the subjunctive is something like "It was necessary that you would speak."
Past imperfect implies the action was not complete, and subjunctive weakens it even more. Maybe even though it was necessary, you did not speak.
Even though this is the Subjunctive Imperfect tense, I assume that it is still about the presence of doubt in the given statement. There is no doubt in the above sentence. So I must assume that the tense is triggered by "che" regardless of its degree of definitiveness?
Also, I believe that the Italian sentence also mean "It was necessary for YOU to speak." It would make of itself a better learning tool if Duo listed ALL the correct translations.
In translating, you sometimes have to take a lot of liberty with the translation, in order for it to sound good in the language you're translating to. Context has a lot to do with it.
If this sentence were translated literally, it would go something like this: "It was necessary that I/you were speaking." That doesn't make that much sense in English, so you have to approximate it, give it it's best meaning closing to what the Italian means. Sometimes that means using "would", sometimes "was", sometimes "is", and sometimes something else.
However, becoming fluent in a language means learning to think in that language. You don't translate it in your mind as you hear or read it, you simply understand it, like you understand your native tongue. That only comes with experience and exposure and practice and study, hopefully some of it tutored by an expert. When you become fluent, you'll stop asking many of these questions, because it will make sense.
Which isn't to say you have to give up trying to figure out how it fits together in terms of your own language - it's just a word of encouragement that it will all get a lot more clear the more you work on it.