Warning this voice needs a \voiceXx or \shiftXx setting

If notes from two different voices with stems in the same direction occur at the same musical moment, but the voices have no voice-specific shifts specified, the warning message ‘warning: this voice needs a \voiceXx or \shiftXx setting’ will appear when compiling the LilyPond file. This warning will appear even when the notes have no visible stems, e.g., whole notes, if the stems for shorter notes at the same pitch would be in the same direction.

Remember that the stem direction depends on the position of the note on the staff unless the stem direction is specified, for example by using \voiceOne, etc. In this case the warning will appear only when the stems happen to be in the same direction, i.e., when the notes are in the same half of the staff.

By placing the notes in voices with stem directions and shifts specified, for example by using \voiceOne, etc., these warnings may be avoided.

Notes in higher numbered voices, \voiceThree, etc., are automatically shifted to avoid clashing note columns. This causes a visible shift for notes with stems, but whole notes are not visibly shifted unless an actual clash of the note heads occurs, or when the voices cross over from their natural order (when \voiceThree is higher than \voiceOne, etc.).

See also

Explicitly instantiating voices, Real music example, Single-staff polyphony, Collision resolution.

LilyPond — Usage v2.25.8 (development-branch).