Simple Question

[Ron]

I have not got a clue whether this is where I should be asking this 
question. But here goes.

Please let me know if this should posted elsewhere.

I have a very simple question: I am trying to add a second line to the 
song I am writing. I can get the second line to appear, but the first 
line plays at the same time as the second line. How do I separate the 
two lines?

Here's what I have written so far:
\version "2.10.20"
\header{ title = "Listen to the Rain" }
uppera = \relative c'' {
\clef treble
\key bes \major
\time 4/4
\tempo 4=120

g g a bes d2 c2 bes1
}

lowera = \relative c {
\clef bass
\key bes \major
\time 4/4

g4 g a bes d2 c2 bes1
}
texta = \lyricmode {
Lis -- ten to the ra -- a -- ain
}

upperb = \relative c'' {
\clef treble
\key bes \major
\time 4/4

bes4 bes bes a g ees2. r1
}

lowerb = \relative c {
\clef bass
\key bes \major
\time 4/4

bes4 bes bes a g ees2. r1
}
textb = \lyricmode {
com -- ing down from the throne
}

\score {
<<
\new Staff = uppera { \new Voice = "singer" \uppera }
\new Lyrics \lyricsto "singer" \texta
\new Staff = lowera {
\clef bass
\lowera
}
>>
<<
\new Staff = upperb { \new Voice = "singer" \upperb }
\new Lyrics \lyricsto "singer" \textb
\new Staff = lowerb {
\clef bass
\lowerb
}
>>

\layout {
\context { \Staff \accepts "Lyrics" }
\context { \Lyrics \consists "Bar_engraver" }
}

\midi { }
}

Thank you,
Ron