Serviceberry (Juneberry, Amelanchier sp.) might be a good one. It flowers early, gets colorful fruit in the summer, decent fall color, and has interesting structure and bark during the winter. There are various species and cultivars, some with better fall color than others. Local nurseries could probably suggest ones that do best in your area.

'Princess Kay' plum. Looks good year-round. Wonderfull scent to the flowers. Native to your area, so it's hardy for you. But not multistemmed.

Any of the small magnolias meet all these criteria. 'Leonard Messel' is outstanding

Dwarf Chinkapin Oak (Quercus prinoides) fits that description to a "t."

OMG, they all sound fantastic - and I would never have thought of any of them.

Wish I didnt have such a TINY yard!

I like pagoda dogwood, Cornus alternifolia. It grows wild around here, so should be hardy for you. While not necessarily narrow, it's about the right height, multistemmed, and can be pruned to reduce the number of stems so it isn't as bushy. It has elderberry-like flowers in the spring (not largebract-flowers like C. kousa or C. florida), nice berries with bright red stems that ripen to dark purple in August, and soft yellows, reds and purples in the fall foliage. Winter stem silouettes are nice as well. No one aspect is totally stunning, but it has true year-round interest and the birds love it.

Check out some of the tree lilacs. I am not sure of there zone hardiness but some selections have nice bark. You can also check on Paperbark Maple and Korean Stewartia. If they will do well in your locations they are two of the nicest smaller 4 season trees.

David