Problem starting multiple voices

[Ed Keith]

I'm new to lilypond. I'm trying to engrave a simple song with four voices on 
two staffs (saprano and alto on the treble staff and tenor and bass on the 
bass staff).

The problem is the the two voices on a staff do not come in on the same 
note, but lilypond will not seem to work right unless they do. I have 
worked around the problem by putting in a leading rest, but this seems like 
a crufty hack, and to screws up the lyrics.

What is the correct way to do this?

Thank you very much,

   -EdK