Technically, you can overseed any cool-season grass with any other cool-season grass.

But...you're going to get some warnings from the regulars/experts here, I think...about ryegrass, in particular.

And the thing that comes to mind to me, is the red fescue being prone to burnout in the heat...I've had horrible luck with fine fescue in CT in the summer, let alone Indiana. And ryegrass isn't a whole lot better in that respect, in my experience...it's still fairly prone to burning up in the heat. Honestly, the tall fescue is probably the best grass for your climate...much more heat and drought tolerant than rye, and especially fine fescues.

Why not get some of the latest turf type tall fescue (TTTF) cultivars and overseed with those instead?

Is the area sunny or shade? How did you come to the decision of a rye/fine fescue mix?

Unfortunately, your approach is not a good idea. Red fescue, more commonly referred to as fine fescue, are used in areas of moderate to heavy shade where other grasses won't due so well. Kentucky Bluegrass and Ryegrass being at the top of the list. Turf Type Fescues do best in sun, but are the most shade tolerant and can take a good amount of shade.

Overseeding with a grass that loves shade (Red Fescue) and the opposite counterpart that loves sun and is not very shade tolerant at all (Rye) doesn't make much sense. This is where the question comes in, what is your yard, shade or sun?

...KBG mixes commonly have rye and red fescue in them to gradually blend into areas of shade. But to overseed a fescue lawn with just the two doesn't make sense.

Not to mention how terrible a fine fescue and course fescue will look in the same lawn.

I would assume, due to your wide blade complaint, that you have an older fescue type grass. Newer turf type fescues are much more fine and fairly comparable to the thinner blades of KBG and Rye.

Thanks for replies.
yard gets 6-8 hours of sun in afternoon in summer.

Yes, It is a Scotts mix called 'Sun and Shade' it has some KBG mixed but it is mainly Rye Grass and Red Fescue.

Most around here, including me, will try to encourage people to avoid "scotts" grass seed mixes. They are far from being good by any means. I was trying to find the % of the Sun & Shade you quoted and all I could find is this..

"Scotts Select Turf "Sun and Shade" (50% Boreal creeping red fescue, 35% Ragnar II perennial ryegrass, 15% Alene Kentucky bluegrass). Boreal is a fancy name for common creeping red fescue. Although it is adapted to shady growing conditions, Boral has none of the bred-in advantages of improved fine fescue varieties. Ragnar II, like all perennial ryegrasses, has no shade tolerance. Alene is a common type bluegrass that ranks at the bottom of the NTEP trials."

A further explanation of my statement above.

6-8 hours of sun is the standard for "Full sun", against the misconception of full sun truly being sun all day long. You could really use any of the three cool season grasses and do not need the fine fescues. However, like I said before, any of the newer varieties are not going to visually blend well if you have an old wide blade fescue. ..I also didn't mention the different growing rates if you are to put a KBG or RYE on the fescue. A few days after cutting, it will look uneven.

Ultimately the best thing to do would be to kill of the whole thing and start over (assuming you do have an old course tall fescue), but if your really against that, I'd say to overseed it with a turf type fescue.

Go to a local garden center for better seed.