O vocalista ensaiou, só que desafinou no solo.

Só que means something like but, except that, or only... in the sense of a contrast.

In this sentence, it connects two ideas:

• O vocalista ensaiou = the singer practiced / rehearsed
• só que desafinou no solo = but he sang out of tune in the solo

So it introduces an unexpected contrast: he practiced, but he still got the solo wrong.

In everyday Brazilian Portuguese, só que is very common and often sounds more conversational than mas.

Yes, in most cases you can:

• O vocalista ensaiou, mas desafinou no solo.

This means almost the same thing.

The difference is mainly tone:

• mas = standard, neutral but
• só que = a bit more informal/conversational, often with a stronger feeling of and yet / but then

So both are correct, but só que sounds very natural in spoken Brazilian Portuguese.

Ensaiou is the past tense of ensaiar.

Depending on context, ensaiar can mean:

• to rehearse
• to practice
• sometimes to try out or prepare

In a musical context like this, ensaiou usually means rehearsed or practiced.

Examples:

• A banda ensaiou ontem. = The band rehearsed yesterday.
• Ela ensaiou a música várias vezes. = She practiced/rehearsed the song several times.

Both ensaiou and desafinou are in the pretérito perfeito (simple past / preterite).

This tense is used for completed actions in the past.

So:

• ensaiou = he rehearsed / practiced
• desafinou = he sang out of tune / went off-key

The sentence describes two finished events:

1. He practiced
2. Then he went off-key in the solo

For -ar verbs, the ele/ela/você form in the preterite often ends in -ou:

• ensaiar → ensaiou
• desafinar → desafinou
• cantar → cantou

Desafinou comes from desafinar, which means to go out of tune, to sing/play off-key, or to be out of tune depending on context.

Here it means the vocalist did not hit the notes correctly during the solo.

Related words:

• afinado = in tune
• desafinado = out of tune
• afinar = to tune / to get in tune
• desafinar = to go out of tune / sing or play out of tune

Example:

• O violão está desafinado. = The guitar is out of tune.
• Ela desafinou na apresentação. = She sang off-key during the performance.

No solo means in the solo or during the solo.

No is a contraction of:

• em
  • o = no

So:

• no solo = em o solo = in the solo

This kind of contraction is extremely common in Portuguese:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

Examples:

• na música = in the song
• no show = at the show / in the concert
• na apresentação = in the performance

Yes, here solo has basically the same meaning as in English music vocabulary: a part where one singer or instrumentalist performs alone or stands out.

So desafinou no solo means he went off-key during the solo part.

Be aware that solo can also mean soil/ground in other contexts in Portuguese, but in this sentence the musical meaning is clear.

Examples:

• Ela cantou um solo lindo. = She sang a beautiful solo.
• O guitarrista errou no solo. = The guitarist made a mistake in the solo.

Portuguese often uses definite articles more than English does.

So O vocalista literally means the vocalist / the singer.

In context, it usually refers to a specific known person, such as the singer of a band already being discussed.

English sometimes drops the article more easily, but Portuguese commonly keeps it:

• O vocalista chegou cedo. = The singer arrived early.
• A guitarrista errou a entrada. = The guitarist missed the cue.

Without the article, vocalista by itself would usually sound less natural as a full subject in a normal sentence.

No. Vocalista can refer to either a male or female vocalist.

The word itself often stays the same:

• o vocalista = the male vocalist
• a vocalista = the female vocalist

So the article tells you the gender here, not the ending -ista.

This is common with many Portuguese nouns ending in -ista:

• o artista / a artista
• o pianista / a pianista
• o turista / a turista

The comma helps separate the two clauses:

• O vocalista ensaiou
• só que desafinou no solo

This is very natural in Portuguese when linking two complete ideas with a contrasting connector like mas or só que.

You will often see:

• Ele estudou, mas foi mal na prova.
• Ela treinou, só que perdeu o jogo.

The comma makes the contrast clearer and matches normal written style.

A natural Brazilian Portuguese pronunciation would sound roughly like:

O vocalista ensaiou, só que desafinou no solo.

Helpful pronunciation notes:

• vocalista → stress on lis: vo-ca-LIS-ta
• ensaiou → roughly en-sai-OU
• só → open ó, like a stressed saw-type vowel
• que in só que → usually sounds like kee or a short ki
• desafinou → de-sa-fi-NOU
• solo → SO-lo, stress on the first syllable

In connected speech, só que is often pronounced smoothly together, almost like one chunk:

• sóqui

So the rhythm is something like:

• O vocalista ensaiou, sóqui desafinou no solo.