Я вряд ли смогу забыть тот последний аккорд: едва он прозвучал, как в зале начались аплодисменты.

Вряд ли is a set phrase meaning something like hardly, unlikely, or I very much doubt that.

In this sentence, Я вряд ли смогу забыть... means I will hardly be able to forget..., which in natural English is closer to I’m unlikely to ever forget... or I can hardly imagine forgetting....

A few useful points:

• Вряд ли usually goes before the verb or before the part of the sentence it modifies.
• It does not change form.
• It often expresses the speaker’s doubt about a future possibility.

So:

• Я вряд ли смогу забыть... = I’m unlikely to be able to forget...

Both are possible in Russian, but they are not exactly the same.

• Я забуду = I will forget
• Я смогу забыть = I will be able to forget

The sentence uses смогу забыть because it emphasizes ability/possibility, not just the future event itself. The speaker is saying that forgetting that chord is so difficult that they probably won’t even be able to do it.

So the nuance is stronger:

• Я не забуду = I won’t forget.
• Я вряд ли смогу забыть = I will probably not even manage to forget.

Russian aspect is important here.

• забыть = perfective, a completed act of forgetting
• забывать = imperfective, the process or repeated habit of forgetting

After смочь in this sentence, the speaker is talking about whether they will be able to perform the act of forgetting at all. That is a single completed result, so забыть is the natural choice.

Compare:

• смогу забыть = will be able to forget
• смогу забывать would sound odd here, because it suggests being able to be forgetting repeatedly or have the habit of forgetting, which is not the idea.

Тот literally means that, but in real usage it often adds emotional or contextual emphasis.

Here, тот последний аккорд is not just that last chord in a neutral pointing sense. It can also suggest:

• that particular last chord
• that memorable final chord
• the very last chord we both know I mean

So тот makes the phrase more vivid and specific. Without it:

• последний аккорд = the last chord
• тот последний аккорд = that last chord, that particular unforgettable final chord

Because it is the direct object of забыть, and аккорд is an inanimate masculine noun.

For inanimate masculine nouns:

• nominative singular: аккорд
• accusative singular: аккорд

So the accusative looks exactly like the nominative.

The adjective agrees with it:

• тот последний аккорд

If this were an animate masculine noun, the accusative would often match the genitive instead, but аккорд is inanimate.

This is a common Russian pattern meaning hardly had ... when ... or more naturally as soon as ... , ....

In the sentence:

• едва он прозвучал, как в зале начались аплодисменты

the meaning is:

• hardly had it sounded when applause began in the hall
• or more naturally: as soon as it sounded, applause started in the hall

A few important things:

• едва literally relates to barely / hardly
• как introduces the next event
• together they show that the second event happened almost immediately after the first

This structure is quite literary or formal compared with the simplest everyday как только.

Yes. A very close alternative would be:

• Как только он прозвучал, в зале начались аплодисменты.

That is often more straightforward for learners.

The difference is mostly stylistic:

• как только = neutral, very common, direct
• едва ..., как ... = more expressive, often a bit more literary, emphasizing immediacy

So the original version sounds slightly more dramatic and elegant.

Прозвучал is the past masculine singular form of the perfective verb прозвучать.

The perfective is used because the sentence refers to a completed event:

• the chord sounded
• then applause started

The sounding of the chord is treated as a finished whole, a single event that triggered the next event.

If you used the imperfective звучал, it would suggest an ongoing process:

• едва он звучал... would not fit well here

because the meaning is not while it was sounding, but once it had sounded / as soon as it sounded.

It refers back to тот последний аккорд.

In Russian, nouns have grammatical gender, and аккорд is masculine, so the pronoun is он.

So the structure is:

• тот последний аккорд → masculine singular
• он прозвучал = it sounded

Even though English uses it, Russian uses the pronoun that matches grammatical gender.

В зале means in the hall.

Here:

• в = in
• зале = prepositional singular of зал

The preposition в can take different cases depending on meaning:

• в зал (accusative) = into the hall, direction
• в зале (prepositional) = in the hall, location

Since the sentence describes where the applause began, not motion into the hall, Russian uses the prepositional case:

• в зале начались аплодисменты

Because аплодисменты is a plural noun, and the verb agrees with it in number.

• аплодисменты = applause, clapping
• grammatically, it is plural in Russian
• therefore the verb must also be plural: начались

So:

• начались аплодисменты = applause began

Even though English applause is usually treated as singular, Russian uses the plural noun аплодисменты.

Russian commonly uses аплодисменты as a plural noun to refer to applause or clapping as a collective event.

This is one of those cases where Russian and English organize the idea differently:

• English: applause is usually an uncountable singular noun
• Russian: аплодисменты is a plural noun

So learners should think of it less as a word-for-word match and more as the normal Russian way to express the idea.

You may also see:

• раздались аплодисменты = applause broke out / applause was heard
• бурные аплодисменты = loud applause / enthusiastic applause

The colon introduces an explanation or expansion of the first statement.

The first part says:

• Я вряд ли смогу забыть тот последний аккорд

Then the part after the colon explains why the speaker will not forget it:

• едва он прозвучал, как в зале начались аплодисменты

So the colon works like:

• I’m unlikely to forget that final chord: as soon as it sounded, applause began in the hall.

Russian often uses a colon this way to connect a statement with its reason, explanation, or vivid elaboration.

The word order is normal and stylistically natural.

Russian word order is more flexible than English, but here the structure is quite standard:

• едва он прозвучал = as soon as it sounded
• как в зале начались аплодисменты = when applause began in the hall

Placing в зале before начались аплодисменты helps set the scene first: in the hall, applause began.

Russian often uses word order to manage emphasis and flow rather than strict grammatical roles alone. In this sentence, the order feels smooth and narrative.

Yes. Russian could also say:

• ...как аплодисменты начались в зале
• or more naturally in some contexts, ...как в зале зазвучали аплодисменты

But the original как в зале начались аплодисменты sounds very natural because it presents the location first and then the event. That creates a nice dramatic effect: first the hall, then the applause breaking out.

So this is not about correctness versus incorrectness; it is mostly about style, rhythm, and emphasis.