La mezcla incluye la sintonía.

Because both nouns are feminine singular in Spanish:

• la mezcla = the mix / the mixture
• la sintonía = the tune / the theme tune / the station jingle, depending on context

In Spanish, nouns usually need an article more often than in English, especially when talking about a specific thing.

Incluye is the present tense form of the verb incluir.

Here, the subject is la mezcla, which is third person singular, so the verb must match it:

• incluir = to include
• la mezcla incluye = the mix includes

So incluye means includes.

The subject is la mezcla because it is the thing doing the action of including.

A simple way to check:

• What includes something? La mezcla
• What is included? La sintonía

So:

• la mezcla = subject
• incluye = verb
• la sintonía = direct object

It depends on context. In Spain, sintonía can mean several related things, such as:

• a tune
• a theme tune
• a signature melody
• a radio or TV jingle
• sometimes tuning, in technical contexts

In a sentence like this, it often sounds like the tune/theme tune is included in the mix.

The accent mark shows the stress: sin-to-NÍ-a.

It also helps show that í-a is pronounced in two syllables, not merged into one. So the word has four syllables:

sin-to-ní-a

Without the accent, the pronunciation rules would suggest a different stress pattern.

In most of Spain, z is pronounced like the th in think.

So mezcla sounds roughly like:

METH-kla

In many parts of Latin America, it would sound more like:

MES-kla

Since you asked about Spanish from Spain, the th sound is the standard answer.

Because la sintonía is a thing, not a person.

The personal a is normally used before a specific human person (and sometimes pets or personified beings). For example:

• Veo a María
• Escucho a mi profesor

But with things, you usually do not use a:

• La mezcla incluye la sintonía

So this sentence is correct without it.

Normally, no. That sounds incomplete or unnatural in standard Spanish.

Spanish uses articles more often than English. In this sentence, the articles help identify both nouns naturally:

• La mezcla incluye la sintonía

If you remove them, it sounds more like note-taking, a headline, or very unnatural speech.

Often, yes. Mezcla can be used for:

• a mixture
• a blend
• a mix, including an audio mix in music or sound production

So in the right context, la mezcla can absolutely refer to the mix.

Yes, but the original order is the most neutral and natural:

• La mezcla incluye la sintonía

You might also see:

• La sintonía la incluye la mezcla

But that sounds marked or unusual unless you are emphasizing la sintonía specifically.

For a learner, the basic subject + verb + object order is best:

• La mezcla
  • incluye
    • la sintonía

In Spain, roughly:

la METH-kla in-KLOO-ye la sin-to-NEE-a

A few pronunciation notes:

• mezcla: the z is like th in think
• incluye: the y here sounds a bit like an English y
• sintonía: stress on ní

A more syllable-by-syllable guide: la | meth-kla | in-clu-ye | la | sin-to-ní-a