Kung sakaling walang reserbasyon, kumanta tayo ng karaoke sa bahay.

Kung sakaling means something like if ever, in case, or supposing that. It makes the condition sound a little more hypothetical or uncertain.

• Kung = if
• Kung sakaling = if it so happens that... / in case...

So:

• Kung walang reserbasyon... = If there is no reservation...
• Kung sakaling walang reserbasyon... = If by any chance there is no reservation...

The version with sakaling feels a bit softer and more tentative.

Walang is the form of wala used before a following word.

• wala = none / not there / does not exist
• walang = wala
  • linker -ng

So:

• may reserbasyon = there is a reservation
• walang reserbasyon = there is no reservation

This is more natural than using hindi, because wala is used for non-existence or absence.

Filipino often does not need a separate word like English there is or there are.

Instead, it uses:

• may = there is / there are / has
• wala = there is no / there are no / does not have

So walang reserbasyon already means there is no reservation.
You do not need another word corresponding to English there is.

Yes. Reserbasyon is a borrowed word, ultimately from Spanish and very close to English reservation.

This is very common in Filipino. Many everyday words are borrowed or adapted from Spanish and English. So a learner should not be surprised by forms like:

• reserbasyon
• istasyon
• ospital
• telepono

Reserbasyon is a normal, natural Filipino word.

This is a very common question.

For many -um- verbs in Filipino, the base/infinitive form and the completed form can look the same. So kumanta can mean different things depending on context:

• kumanta = to sing
• kumanta = sang
• kumanta tayo = let’s sing

Here, because it is followed by tayo and comes after a conditional phrase, it is understood as a suggestion: let’s sing.

Compare:

• Kumanta ako kahapon. = I sang yesterday.
• Gusto kong kumanta. = I want to sing.
• Kumanta tayo. = Let’s sing.

So context is very important.

Because tayo includes the person being spoken to.

• tayo = we, including you
• kami = we, excluding you

Since the speaker is inviting the listener to join, tayo is the correct pronoun.

• Kumanta tayo = Let’s sing
• Kumanta kami = We sang / We will sing, but not with you

This inclusive/exclusive distinction is very important in Filipino.

Here, ng marks the non-subject object or complement of the verb.

In kumanta ng karaoke, ng karaoke is what is being sung or performed. In casual English, the whole phrase means something like sing karaoke or do karaoke singing.

A very literal breakdown is:

• kumanta = sing
• ng karaoke = karaoke / karaoke songs

So ng is functioning somewhat like an object marker here.

Both are understandable, but they have slightly different feels.

• kumanta ng karaoke focuses on the act of singing
• mag-karaoke focuses on doing karaoke as an activity

So if you want the most natural casual phrasing, many speakers might say:

• Kung sakaling walang reserbasyon, mag-karaoke tayo sa bahay.

But the original sentence is still understandable and acceptable. It just emphasizes singing a bit more.

Because verb-first or predicate-first order is very common in Filipino.

So kumanta tayo is a natural structure:

• kumanta = predicate/verb
• tayo = the actor

English usually prefers subject + verb, but Filipino often uses verb + subject.

That is why kumanta tayo ng karaoke sa bahay sounds normal.

A reordered version like tayo ay kumanta... is possible in some contexts, but it sounds more formal or more like a plain statement, not as natural for a suggestion like let’s sing.

Sa bahay means at home or in the house, depending on context.

• sa = in / at / to
• bahay = house / home

In this sentence, sa bahay most naturally means at home.

You do not always need to add a possessive like natin or ko if the meaning is already clear from context. But you could say:

• sa bahay natin = at our house / at our home
• sa bahay ko = at my house

So the original sentence leaves that part general or context-dependent.

Yes. Here are some common alternatives:

• Kung walang reserbasyon, kumanta tayo ng karaoke sa bahay.
  This removes sakaling and sounds simpler.

• Kung sakaling walang reserbasyon, mag-karaoke tayo sa bahay.
  This may sound more natural if you mean the activity in general.

• Kapag walang reserbasyon, mag-karaoke tayo sa bahay.
  This changes the nuance slightly. Kapag can sound more like when/whenever rather than a more uncertain if.

So the original sentence is fine, but there are several natural ways to express the same idea with slightly different shades of meaning.