If the singer wants it in Ab, use the computer ‘cause it will end up in G, A, Bb, or B.

I remember the first time this happened t me. I was so hungry for work I kept my mouth shut and recopied the parts myself. Invariably, vocalists will either change their minds, have bad information from an accompanist, or have a voice change between the time you start the chart and when you finish.

Yes, somewhat facetious but too many times fact than fiction. Notation programs can be a bitch to use and take longer than pencil & paper, but the advantages outweigh those disadvantages.