Когда метроном работает, мне легче держать ритм.

Because Russian often uses an impersonal construction for expressions like it is easier for me.

• мне легче literally means to me, [it is] easier
• English uses I: I can keep the rhythm more easily
• Russian uses the dative case: мне

So:

• я = I
• мне = to me / for me

This pattern is very common:

• Мне трудно понять. = It’s hard for me to understand.
• Мне интересно. = It’s interesting to me / I’m interested.
• Мне легче работать утром. = It’s easier for me to work in the morning.

Легче is the comparative form of легко or лёгкий, and here it means easier.

In this sentence, it works as a predicative word in an impersonal structure:

• мне легче держать ритм = it is easier for me to keep the rhythm

Compare:

• легко = easily / easy
• легче = more easily / easier

Examples:

• Мне легко петь. = It’s easy for me to sing.
• Мне легче петь с метрономом. = It’s easier for me to sing with a metronome.

So легче is not describing a noun here. It is part of the whole idea it is easier.

Russian often omits the present-tense form of "to be".

In English, you say:

• It is easier for me...

In Russian, you usually just say:

• Мне легче...

There is no present-tense есть in normal sentences like this.

So the sentence is completely natural without any separate word for is.

Работает is the present tense of работать and means works / is working.

Here it fits because the sentence describes a general situation or a repeated condition:

• Когда метроном работает, мне легче держать ритм.
• When the metronome is on / working, it’s easier for me to keep the rhythm.

Russian present tense can cover both:

• is working right now
• works / whenever it works as a general fact

So this form is very natural here.

Because the sentence talks about an ongoing state or process, not a single completed action.

• работать = imperfective, focusing on the activity itself
• сработать / заработать would change the meaning

Here, the idea is:

• while the metronome is functioning
• whenever the metronome is on

That calls for the imperfective работает.

After words like легко, трудно, легче, лучше, полезно, Russian often uses an infinitive.

So:

• мне легче держать ритм
• literally: for me [it is] easier to keep the rhythm

This is a very common pattern:

• Мне трудно понять. = It’s hard for me to understand.
• Ему легче читать утром. = It’s easier for him to read in the morning.
• Нам лучше подождать. = It’s better for us to wait.

So держать is here because Russian is saying easier to keep.

Yes, держать ритм is a normal expression meaning to keep the rhythm.

• держать literally means to hold
• but in many contexts it means to maintain or keep

So:

• держать ритм = keep the rhythm
• держать темп = keep the tempo
• держать равновесие = keep one’s balance

It is very similar to English, where keep also has a broader meaning than physically holding something.

Ритм is in the accusative case because it is the direct object of держать.

You are keeping something:

• держать что? → ритм

For this noun, the accusative looks the same as the nominative because:

• ритм is an inanimate masculine noun
• inanimate masculine nouns usually have the same form in nominative and accusative singular

So:

• nominative: ритм
• accusative: ритм

Because Когда метроном работает is a subordinate clause introduced by когда.

Russian normally puts a comma between the subordinate clause and the main clause:

• Когда метроном работает, мне легче держать ритм.

This is similar to English when the when-clause comes first:

• When the metronome is working, it’s easier for me to keep the rhythm.

If you reverse the order in Russian, the comma still stays:

• Мне легче держать ритм, когда метроном работает.

It can suggest either, depending on context.

In this sentence, it most naturally sounds like a general condition, so English could understand it as:

• when
• or whenever

That is because the sentence describes a repeated or typical situation, not just one single moment.

So the idea is roughly:

• whenever the metronome is working, it is easier for me to keep the rhythm

Yes. Russian word order is flexible.

You can also say:

• Мне легче держать ритм, когда метроном работает.

This version may sound a little more natural in some contexts because it presents the main point first:

• It’s easier for me to keep the rhythm...
• ...when the metronome is working.

The original version is also completely correct. The difference is mostly about focus and flow, not grammar.

The stressed syllables are:

• когда́
• метроно́м
• рабо́тает
• мне
• ле́гче
• держа́ть
• ри́тм

So one helpful stress-marked version is:

• Когда́ метроно́м рабо́тает, мне ле́гче держа́ть ри́тм.

A few notes:

• что is not in this sentence, so no special pronunciation issue there.
• In careful speech, работает is pronounced with four syllables: ра-бо-та-ет.
• ритм is short and can feel awkward at first for English speakers because of the consonant cluster.

Sometimes, but the meaning changes a little.

• Когда метроном работает = when / whenever the metronome is working
• Если метроном работает = if the metronome is working

Когда sounds more like a regular time-based situation. Если sounds more conditional.

In this sentence, когда is the better choice because the speaker is talking about what happens during that situation, not setting up a hypothetical condition.

No, я легче держать ритм would be incorrect.

Russian does not normally express this idea with я + легче + infinitive.

You need the impersonal pattern:

• мне легче держать ритм

That is the standard way to say it is easier for me to keep the rhythm.

If you want a more personal structure, you would usually need a different wording, for example:

• Я лучше держу ритм, когда метроном работает.
• I keep the rhythm better when the metronome is working.

That is grammatical, but it is not the same structure as the original sentence.