Learn Hardcore Spanish (Latin America): Si no oyes el timbre, te mando un mensaje. - If you don’t hear the doorbell, I’ll send you a message.

After si in real, likely conditions, Spanish uses the present indicative, not the subjunctive: Si no oyes...
Use the imperfect subjunctive only for hypothetical/unreal conditions: Si no oyeras el timbre, te mandaría un mensaje.
For past, contrary-to-fact: Si no hubieras oído el timbre, te habría mandado un mensaje.

Why is it te mando (present) instead of te mandaré (future)?

Spanish often uses the present to refer to the future in conditional contexts.
Te mandaré is also correct but sounds more formal or like a firm promise. Te mando is more casual/immediate.
All of these are fine, with slight nuance: Si no oyes..., te mando/te mandaré/te voy a mandar...

Can I use escuchas instead of oyes? What’s the difference between oír and escuchar?

oír = to hear (perceive sound, involuntary); escuchar = to listen (pay attention, intentional).
Si no oyes el timbre is neutral: you simply don’t hear it. Si no escuchas el timbre suggests you aren’t paying attention.
Both appear in everyday speech; oír is more precise here.

What exactly does timbre mean in Latin America?

Typically “doorbell,” and by extension a bell/buzzer (e.g., school bell).
In some places it can also mean a “stamp” (rubber stamp or postage), but context clarifies.
Other terms you may hear: campanilla/campana, portero eléctrico (intercom), regional chicharra.

Why is there a comma after the si-clause? Can I put the si-clause at the end?

If the subordinate clause comes first, Spanish uses a comma: Si no oyes el timbre, ...
If it comes second, usually no comma: Te mando un mensaje si no oyes el timbre.
Both orders are natural.

Is te the direct object here? Why te and not le?

Te is the indirect object (recipient, “to you”). The direct object is un mensaje.
With formal usted, use le: Si no oye..., le mando un mensaje.
With ustedes, use les: Si no oyen..., les mando un mensaje.

How would this change with vos (voseo) in parts of Latin America?

Present with vos: vos oís. Sentence: Si no oís el timbre, te mando un mensaje.
The object pronoun stays te with vos.
Affirmative imperative for vos: oí (e.g., ¡Oí el timbre!).

Is it correct to say al timbre after oír?

Could I say te voy a mandar or voy a mandarte instead?

Yes. Both are standard: Te voy a mandar un mensaje / Voy a mandarte un mensaje.
With infinitives/gerunds, pronouns can go before the conjugated verb or attached to the infinitive/gerund; both are correct.

How is oír conjugated in the present? Why oyes?

How do you pronounce oír and oyes? Any regional notes?

oír: stress the second syllable (the accent shows it).
oyes: two syllables, stress on the first. The letter y can sound like a soft “y,” or like “zh/sh” in parts of Argentina/Uruguay.
timbre: stress on the first syllable; mensaje: stress on the second.

Can I drop the article and say te mando mensaje?

Standard is te mando un mensaje.
In some informal Mexican usage, te mando mensaje occurs; it’s colloquial/regional.

Does mensaje usually mean a text message?

In everyday Latin American speech, mensaje often implies a text/WhatsApp/DM unless context says otherwise.
Be specific if needed: mensaje de texto, WhatsApp, DM, correo (email).

What if I mean “If the doorbell doesn’t ring,” not “If you don’t hear the doorbell”?

Use sonar (to ring): Si el timbre no suena, te mando un mensaje.
Original: focus on the person’s hearing; this version: focus on the bell’s functioning.

Why not use the future after si, like Si no oirás...?

Spanish normally avoids the future tense in the si-clause. Use the present: Si no oyes...
The future can appear in the main clause: Si no oyes..., te mandaré un mensaje.

Is mandar ever “to order/command”? Any ambiguity here?

Yes, mandar can mean “to order,” but with a direct object like un mensaje, it means “to send.”
Enviar is a fully synonymous, slightly more formal option: te envío un mensaje.

Why isn’t the subject pronoun tú used?

Spanish drops subject pronouns when the verb ending makes the subject clear. oyes already signals tú.
Add tú only for emphasis or contrast: Si tú no oyes el timbre, ...

What does oye mean as an interjection? Is it related?

Oye is the tú form of oír, and it’s also used as an interjection meaning “hey, listen.”
Here, oyes is simply the verb in a conditional clause, not the interjection.

Why does si have no accent here? What’s the difference between si and sí?

si (no accent) means “if” and introduces conditions, as in this sentence.
sí (accent) means “yes,” or functions as a reflexive intensifier (e.g., lo hizo por sí mismo).
Only si (no accent) is used in conditional clauses.