Arturia MatrixBrute User Manual page 21

LFO 1 is five rows down, VCO 1 Pitch is the first column, so simply push the button
where the two intersect. The button lights purple, indicating it's the one that's
selected; if you click on another button to select additional modulation routings,
it'll turn blue to show it's been assigned.
LFO 1 still won't modulate the pitch until you dial in a MOD Amount. Try + or -13,
a fairly radical pitch modulation, so you can hear the effect.
Arturia - MatrixBrute Manual - Guided Tour 15