How to typeset a chord with variable note length in Lilypond?

I am typesetting a score using Lilypond but I am struggling with the following bar:

I tried `<fa la> <<fa4 {la8 sib}>> …` but it does not render properly.

Global settings.

``````\version "2.20.0"
\language "italiano"
``````

Staff settings.

``````\key fa\major
\clef bass
``````
• Since this wasn't called out specifically, you don't have "chords"; you have multiple independent voices, which Lilypond treats differently. – chrylis -cautiouslyoptimistic- Jun 17 '20 at 10:24

While Glorfindel's answer is correct, it's a bit long-winded. Depending on your needs and the rest of the score, you can get the exact same results by simply inputting

``````<<
{
la4 la8 sib
}
\\
{
fa4 fa
}
>>
``````

In other words, you can do this without all of the `\new Voice = "this"` and `\voiceThat` commands.

It looks like you could use some single staff polyphony.

The following should work; it sets up two voices, one with stems up, the other with stems down, so they can play/sing different rhythms.

``````\score {
\new Staff <<
\key fa\major
\clef bass
\new Voice = "first" { \voiceOne la4 la8 sib }
\new Voice = "second" { \voiceTwo fa4 fa }
>>
}
``````

Output:

Putting `\relative do` at the start of each voice keeps the voice in the same octave (in the second voice).
Using `q` to repeat chords is very useful.
``````<<