How to make editor with multiple fonts?

Hi, does anybody know is it possible (and how) to use multiple
fonts in the editor? For example, to specify the font change in a
specific location in a buffer? Or do I need to make my
editor-with-style based on rich-text?

I've played around with rich-text and it appears very useful for text
formatting, but it seems to operate differently than the normal
editor, and I'd like to maintain all the basic editor commands to
keep it backward-compatible.

Any hints would be the most welcome!

Pekka