There's hardly anything new to be done anyway if you ask me, but old + new = new, the order doesn't matter. Is Gorecki's 3rd a Symphony using new techniques or a modern piece using an old approach?
Well, Baroque music leaves quite some space for new things. The harmonic language was quite limited - iminished and dominant 7th chords were used a lot but the piece always stayed in a related key most of the time. Formally there weren't a lot of options: binary or ternary (dance) forms, fugues, canons etc. in comparison to what composers were doing later on. If a baroque piece in sonata form is feasible is open to discussion although I doubt it.
There are also atonal fugues. One important thing to notice is that a lot of counterpoint builds upon the concept of dissonances and their resolution, thus convincing atonal contrapuntal works are very hard to pull off.
Also Peter, serialism uses "old" terms like inversion, retrograde etc, but is still regarded as relatively modern.