Absolutely! That's what the Telharmonic's "FM" input is for. That'll take any modulation input ranging from long LFO curves up into audio-range signals. Running a sine from the STO to the Tel's FM will let you do basic FM against additive spectra. Even better: DON'T connect a CV to the STO, but DO connect one to the Tel. That way, every change in pitch becomes an equally-radical timbral change as well. LOTS of tricks can be done like that, so showing off a single patch is just scratching the surface. For example, you could send that STO sine through a linear VCA, and give the VCA the output of an EG with a slow attack. With that, you'd then have the FM component grow in complexity as the attack ramps up to the sustain level, then tail away on release.
Best suggestion here is this: Rule #1: don't patch an output to an output. Otherwise, go NUTS. See what YOU can come up with. A modular is basically a sandbox for sound...with this sort of a rig, you'll be pulling new sounds out of this box for years!