A voice is the termUsed to describe a unique melodic line or part. Most of the time each staff contains only one voice, but occasionally the need arises to put more than one melodic line on a single staff. One example is two part vocal writing, where the soprano and alto share the same staff. Other examples include keyboard notation, drum notation, and barbershop quartets.
Support of Voices
You can use up to 8 voices for each staff. To notate several different musical lines, as for choral parts, you would enter notes for each part as a separate voice. The notation engineUses the voice designation to determine things like stem direction, beaming patterns, and note groupings. This technique for handling notes and voices keeps each part visually distinct, even though 2 notes might occur at the same time. The default voice when adding notes is All. By default, odd-numbered voices (1, 3, 5, ...) are displayed with stems up and even-numbered voices (2, 4, 6, ...) are displayed with stems down. In a Grand Staff, voices 1-4 areUsed for the treble clef and voices 5-8 (1 L.H. - 4 L.H.) areUsed for the bass clef. If you merge or split staves you will want to do so with these default rules in mind since they greatly affect how the notation will end up.
You can select the voice you want to enter in the main tab "Home" in the group "Voices":
Manipulating Voices Independently
Voices are primarilyUsed for notational purposes, but even so it is sometimes desirable to manipulate the sound of each voice independently. The most common example is when all parts are to be notated in a Grand Staff, but are to be played through different instruments (a piano playing an alto part and a saxophone playing the tenor part). Using the Staff Properties Palette you can specify completely independent MIDI channels and/or devices for each voice on each track. Although unorthodox, you could have voices 1-3 playing as a harmonica on the internal synth, voices 4-6 as an organ on an external keyboard, and voice 7-8 as percussion sounds on a drum machine. Keep in mind that ultimately you are still constrained by the number of independent MIDI channels you actually have. The ability to control the output of each voice makes it easier to manage routing but it does not increase the available MIDI output.