Не успел пианист нажать на клавиши, как в зале стало совсем тихо.

This is a very common Russian pattern meaning no sooner ... than ... or before someone even had time to ... , ... happened.

So:

Не успел пианист нажать на клавиши, как в зале стало совсем тихо.

means something like:

The pianist had barely managed to press the keys when it became completely quiet in the hall.

The idea is that the second event happened almost immediately after, or even before the first one could fully unfold.

A very literal breakdown is:

• не успел = did not have time / did not manage in time
• как = introduces the sudden next event, often like when or than

This construction often gives a vivid, slightly dramatic feeling.

Because успел is past tense, masculine singular, and it agrees with пианист.

• пианист = pianist (masculine singular noun)
• so the verb in the past tense is успел

Compare:

• пианист успел = the male pianist managed
• пианистка успела = the female pianist managed
• пианисты успели = the pianists managed

In Russian past tense, the verb usually agrees in gender and number with the subject.

After успеть, Russian normally uses an infinitive to say what someone managed or failed to manage to do.

So:

• успел нажать = managed to press
• не успел нажать = didn’t have time to press

This is similar to English managed to + verb or didn’t have time to + verb.

Other examples:

• Я не успел поесть. = I didn’t have time to eat.
• Она успела прийти. = She managed to arrive in time.

So нажать is there because it is the action that the pianist did not yet have time to complete.

Because here Russian is talking about a single completed action: to press the keys, not to be pressing or to press repeatedly.

• нажать = perfective, one completed press / the action as a whole
• нажимать = imperfective, process, repetition, or general action

In this sentence, the meaning is that the hall went quiet before the pianist could even perform that single action. That is why perfective нажать fits naturally.

If you used нажимать, it would sound more like focusing on the process of pressing, which is less natural here.

Because нажать на что? takes на + accusative.

So:

• dictionary form: клавиши = keys (plural nominative)
• accusative plural of inanimate nouns is the same as nominative plural
• therefore: на клавиши

This is just how the verb works:

• нажать на кнопку = press the button
• нажать на педаль = press the pedal
• нажать на клавиши = press the keys

So the preposition на here does not mean location. It is part of the verb pattern нажать на ....

Because в зале means in the hall, expressing location.

After в meaning in, Russian uses the prepositional case for location:

• зал = hall
• в зале = in the hall

Compare:

• в комнате = in the room
• в театре = in the theater
• в зале = in the hall

So this part simply tells us where it became quiet.

Because стало тихо is an impersonal way to describe a change of state: it became quiet.

This is extremely common in Russian.

• стало тихо = it became quiet
• стало холодно = it became cold
• стало грустно = it became sad

Here тихо is not an adjective agreeing with зал. It is a predicative adverb/state word describing the general atmosphere.

So:

• в зале стало совсем тихо = it became completely quiet in the hall

If you said зал стал тихим, that would mean something more like the hall became quiet, treating the hall itself as the subject. Grammatically possible in some contexts, but much less natural here. Russian strongly prefers the impersonal atmospheric phrasing.

Because in impersonal constructions like стало тихо, Russian uses neuter singular past tense by default.

There is no normal personal subject here. The idea is not the hall became quiet as a grammatical subject-verb statement. Instead, it is more like things became quiet there or simply it became quiet.

That is why the verb appears in the neuter singular form:

• стало тихо
• стало холодно
• стало темно

This is a standard Russian pattern.

Совсем strengthens the word тихо.

So:

• тихо = quiet
• совсем тихо = completely quiet / perfectly quiet / absolutely quiet

It emphasizes that the hall became very quiet, with no noise left.

Depending on context, совсем can mean:

• completely
• entirely
• totally

Here it clearly means completely.

Because как introduces the second part of the construction не успел ..., как ....

Russian punctuation normally separates these two clauses with a comma:

• Не успел он войти, как все замолчали.
• Не успели мы сесть, как поезд тронулся.

So the comma marks the boundary between:

1. the event that had barely happened or had not yet had time to happen
2. the sudden next event

Yes, that is also possible.

Both of these are natural:

• Не успел пианист нажать на клавиши, как...
• Пианист не успел нажать на клавиши, как...

The version with Не успел first sounds a bit more literary or dramatic, because it puts the focus immediately on the barely had time / no sooner idea.

Russian word order is flexible, and changing it often changes emphasis rather than basic meaning.

It is the same word, but not the same function.

Russian как can mean different things depending on context, including:

• how
• as
• when
• part of fixed constructions such as не успел ..., как ...

In this sentence, it does not mean how. It functions as part of the fixed pattern and is best understood as something like when or than in English:

• No sooner had the pianist pressed the keys than the hall became quiet.

So you should learn не успел ..., как ... as a whole expression.

Yes, slightly.

The construction не успел ..., как ... is very common and fully normal, but it can sound a bit more polished or narrative than plain everyday speech.

In casual speech, someone might also say something like:

• Как только пианист нажал на клавиши, в зале стало совсем тихо.
• Едва пианист нажал на клавиши, в зале стало совсем тихо.

But не успел ..., как ... is still standard and natural, especially in storytelling, written Russian, and expressive speech.