Selecting single voices

It depends upon how the voice was entered on the score. I can think of 3 possible answers off the top of my head. Please attach your score.

If the bass voice is a separate instrument, then View / Mixer allows you to solo it. If it's a separate staff but in the same instrument as other voices, then select the contents of the other staves, press Notes in the Inspector to limit selection to just notes, then uncheck Play. if the bass is a single voice within a staff that also contains other voices, use the same basic technique, but use View / Selection Filter to exclude the bass voice from the selection.