Do you have any advice for people who want to sing and play (bass, for example) at the same time? Or is it just "practice makes perfect" ??
just start doing it. playing and singing together will feel like its own instrument. for bass, you absolutely must play in a band to really get any experience, i think. for piano + singing, for example, that's something that works well all by itself, and i should mention that regardless of vocal, piano in a band and piano outside of a band are also like 2 different instruments (the work is divided completely differently between your hands).  for bass, one of the confusing things you will run into is note duration (length of notes) which is very important for the bass, and it will be confusing at first to get those right while trying to sing something which will have different note durations. but experience will do the trick. will lee did it on TV four days a week for 30 years and he got it down pretty good (well, the singing part wasn't usually on TV, but it happened during the break)