Hey Roger,

Great question! The Thin Lizzy song "Still in Love With You" might be a bad example because it has two extra long solos, plus the rhythm parts are very detailed. But to answer your question "how long to memorize a song," this one could take about 8 hours or more provided you have a good memory and learn the song in small memorized chunks. On the other hand, a song like the Beatles "She Love You" might only take a couple hours.

It gets easier the more you work those memory muscles.

-Dave