Welcome! There are plenty of topics on Alec. You could find them if you do a search with his name.

The quick answer to your question is, no one knows for sure. There are rumors that Alec was the touring musician and Hugh was the studio one but I don't believe that entirely.

My theory is that Hugh was a studio musician that was better at writing some of the bass lines but Alec still played on the majority of the songs.

The best thing about Alec was getting Tico