its like making instruments of some whole parts of the song.
like:

lalalal lallal al lalla la l al lalla llal al
lalalal lallal al lalla la l al lalla llal al
lalalal lallal al lalla la l al lalla llal al
lalalal lallal al lalla la l al lalla llal al

lalala

lalalal lallal al lalla la l al lalla llal al
lalalal lallal al lalla la l al lalla llal al
lalalal lallal al lalla la l al lalla llal al
lalalal lallal al lalla la l al lalla llal al

the "lalalal lallal al lalla la l al lalla llal al" is repeating a lot so you can do it like this:

4x lalalal lallal al lalla la l al lalla llal al

1x alala

4x lalalal lallal al lalla la l al lalla llal al


now you only have 2 instruments.

(dont you think i can sing like a bird)