Musclewood, Pagoda Dogwood, Flowering Dogwood, serviceberry?

Thanks. I will check those out. Never heard of musclewood.

Although it doesn't have fall color, an often overlooked small, narrow tree (maybe 12-15 ft. x 6 ft wide) is Laburnum, or Golden Chain tree. It has long racemes of fragrant yellow flowers in spring, looking like a yellow wisteria blossom. Three leaflets per leaf, so not very dense, and the bark is greenish. Not to be confused with Golden Rain Tree (Koelreuteria paniculata) which is much larger and blooms in summer.

Edlincoln's suggestions will all ultimately get too large for the space unless you choose a flowering dogwood cultivar that has been selected for small size or narrow width, and then I think it will be too dense. I grow and like all of them, but all get wider than your space allows.

Heptacodium miconioides AKA seven son flower will be about the right size and airy enough if pruned to tree form. Late summer flowers and the seeds continue the interest into fall, without seeding around.

You could train one of the larger, stiffer-stemed Hydrangea paniculata AKA panicle hydrangeas as a tree. Look at Limelight, Pinky Winky, and Quickfire. They are sometimes found in nurseries already in tree form, but there is a premium paid for that and you don't have the same control of branch height and form as you would if you did it yourself.

Some of the larger Viburnums will work pruned up as trees. Perhaps Thyme2dig will weigh in on this as she has done some of that in her garden.

A great resource for searching for what you might like is the Missouri Botanic Garden's Plant Finder. You can either put in the name of a plant that's been suggested (scientific names work better than common names IME) and will get an accurate and detailed description of the plant including potential issues, or you can fill in requirements below, leaving anything you don't care about blank, and it will list suggestions.