> Try this with and without the \new Voice commented.
>
> \version "2.25.12"
>
> \language "english"
>
> \score {
> %\new Voice
> <<
> {bf bqf bf}
> {g gqs g}
> >>
> \layout {}
> \midi {}
> }
>
> Obviously you would need to listen to the MIDI output.
This is a limitation of MIDI: You can only have a single pitch bend
per time step per channel. LilyPond's rather primitive MIDI 1.0
output provides no means to circumvent this limitation.
Looking into MIDI 2.0 I see that there exists a 'per-note pitch bend'
feature, so maybe someone is going to implement that in LilyPond.
Werner