Can lilac or buddleja be kept tall but narrow?

[Skiffle]

I am not a gardener as you can no doubt tell from my question. We have a south facing garden, very little shade. I want a plant that will give a bit of dappled shade but not take up too much space. Some of the plants that are decorative and reasonably tall seem to grow as tall as they are wide. Is it possible to prune them back just to grow upwards a bit more, or is that doomed to failure?

If money were no object I'd get a couple of fully grown, small trees, but that would be far too expensive so I'm thinking some reasonably fast growing shrubs might be the best bet.

[ScumbleGoosie]

You can prune them into whatever shape you like. Just bear in mind that the flowers develop on the ends of the branches, so make sure you have enough "outwards" pointing branches at the depth you want, or you will end up with a few very long spindly growths with flowers right at the top where you cant see them!

[DewDr0p]

If you prune eucalyptus hard each spring it will do just what you want and enjoy the sunshine too. Or a bamboo in a massive pot?

I have an Amelanchier shrub which is tall and slim but perhaps not big enough to cast the dappled shade you are after.

Buddleia might work. When you say not take up too much room, how small a footprint are you envisaging?