At this point in our study, it is wise to generally play with only one finger down (unless of course you are playing double stops!) However, there are cases where it makes sense to leave a finger down while you grab a note on another string and it then allows for speed and accuracy in intonation. Ragtime Annie allows for this in the opening part of the tune. It is a good idea to leave your 2nd finger down through the first two measures. This also encourages awesome left hand shape and technique. In the exercise below, try leaving D1 down in measure 1, then D2 in measure 2, etc. Good luck!