Espera el cambio de pareja; si no, perderás el ritmo.

Yes. Espera is the informal singular affirmative imperative of esperar — in other words, a command addressed to tú:

• (tú) espera = wait
• (usted) espere = a more formal wait

So the sentence is talking to one person informally: Wait for the partner change...

Perderás is the simple future form of perder:

• perderás = you will lose

It is used because the sentence is expressing a consequence that will happen if the person does not do the first action:

• si no, perderás el ritmo = if not, you’ll lose the rhythm

Spanish often uses the future like this to show a likely result. You could sometimes hear present tense in similar situations, but perderás sounds very natural here.

Here si no means if not.

• si = if
• no = not

So:

• si no, perderás el ritmo = if not, you’ll lose the rhythm

This is different from sino written as one word.

Difference:

• si no = if not
• sino = but rather / except

Compare:

• Hazlo ahora; si no, será tarde. = Do it now; if not, it’ll be late.
• No quiero té, sino café. = I don’t want tea, but rather coffee.

That distinction is a very common learner question.

The semicolon links two closely connected parts:

• Espera el cambio de pareja
• si no, perderás el ritmo

It works a bit like a stronger comma or a lighter full stop. In English, you might also see:

• Wait for the partner change; otherwise, you’ll lose the rhythm.
• Wait for the partner change. Otherwise, you’ll lose the rhythm.

So the semicolon is mainly punctuation style, not a special grammar point.

Literally, it means the change of partner or the partner change.

In context, this most likely refers to something like dancing, where people switch partners during an activity. Spanish often uses de in this type of phrase:

• cambio de pareja = partner change
• cambio de ritmo = change of rhythm
• cambio de planes = change of plans

So espera el cambio de pareja means wait for the partner change or wait until the partners switch, depending on the context.

Because esperar is normally used without the preposition a when it means to wait for.

So in Spanish:

• esperar algo = to wait for something
• esperar a alguien = to wait for someone

Examples:

• Espero el autobús. = I’m waiting for the bus.
• Espero a Marta. = I’m waiting for Marta.

So espera el cambio de pareja is correct because cambio is a thing, not a person.

Spanish often uses the definite article where English might not.

So:

• perder el ritmo = to lose the rhythm / to lose your rhythm

This is a very common pattern in Spanish, especially with body parts, abstract nouns, and things understood from context.

Other examples:

• levanta la mano = raise your hand
• tengo la garganta seca = my throat is dry
• perdió la paciencia = he/she lost patience

So el ritmo sounds perfectly natural in Spanish.

It can definitely just mean partner.

Although pareja can refer to a romantic partner, it also commonly means a partner in an activity, especially:

• dancing
• sports
• exercises done in pairs
• classroom activities

In this sentence, cambio de pareja almost certainly means switching partners, not changing boyfriend or girlfriend.

Yes. If you wanted the formal version, you would change the verb forms:

• Espere el cambio de pareja; si no, perderá el ritmo.

Compare:

• Espera ... perderás ... = informal singular (tú)
• Espere ... perderá ... = formal singular (usted)

The original sentence is informal.

It can mean both the literal and broader sense of rhythm.

Here, because of cambio de pareja, it probably refers to a dance or coordinated movement, so ritmo may mean:

• musical rhythm
• timing
• flow of movement

Spanish uses ritmo in several ways:

• seguir el ritmo = keep up / keep the rhythm
• perder el ritmo = lose the rhythm / lose the beat
• a buen ritmo = at a good pace

So here it could be understood as you’ll lose the beat or you’ll lose the flow/timing.

The verb esperar can mean both to wait and to hope, depending on context. But in this sentence it clearly means wait.

Compare:

• Espera el cambio de pareja. = Wait for the partner change.
• Espero que venga. = I hope he/she comes.

When esperar means to hope, it often appears with que plus another verb:

• Espero que todo salga bien. = I hope everything goes well.

So although the verb has both meanings, there is no ambiguity here.

Yes, it sounds natural, especially in an instructional setting like dance class, group movement, or any activity where people rotate partners.

The wording is clear and idiomatic:

• Espera el cambio de pareja = a direct instruction
• si no, perderás el ritmo = a natural warning about the consequence

A native speaker might also say similar alternatives, such as:

• Espera al cambio de pareja... in some contexts, especially if the sense is more like wait until the change
• ...o si no perderás el ritmo
• ...si no, te despistarás depending on what exactly is meant

But the given sentence is perfectly good Spanish.