Ugh. 
 
Computer was working fine with Sonar Platinum.  Perfectly.  I HAD to get that stupid Windows Update last month (the big one) and suddenly.... I record audio....open the project the next day.... the damn audio is whole step down.  I reinstall my interface NUMEROUS times, change around my USB ports, do a bunch of other troubleshooting.... nope.  STILL A WHOLE STEP DOWN. 
 
Macs are looking better every day.....

Although this sounds like an audio interface issue, it's worth noting that Toshiba (along with Panasonic, Hewlett Packard / Compaq, Dell, Lenovo and Samsung) have reported problems with the latest Windows 10 Creators version (1709).
 
Supported Toshiba models are listed here
 
Further details and other manufacturers lists are linked from here

DON'T DO THIS!
You know I've been working with PCs for over 20 years and I have thought about throwing one more then once!
Over the last 4 days trying install a good version of win10Pro (log story) and update windows to creator...
I DID! I throw my laptop across the room!
After it sat on the floor for a couple hours... I shut off updates, rebooted and I took a look.
All updates, up to 1703 where good! Window is really massed up!!! 
I'm done updating! All is OK now! it's a good think I throw my crap DELL! and not a real computer! lol
Though not funny!
 
Anyway, go into the device manager and look for Audio try to update them.
Then go down to  sound video game.. and try to update the drivers.
I would delete all the audio drivers and reboot. but that's me...
The have windows fix them if they don't come back right.
You may have drivers overlapping as well so remover any that your not using. 
Also try other audio drivers within Sonar. Set them to mme 1st and see how it goes. then try all the other options...
 
Peace! 
 
 

A friend of mine threw an I7 out his window one time.
Gave it to me, it was a bad hard drive. I charged him 100 bucks and gave him back his 1000 dollar Laptop.
Long story short, I know you didn't mean literally throw it out but just problem solve it one thing at a time.

the whole step down sounds like a sample rate issue...are you sure that your sample rate has not been changed somehow?
 
Check that 1st before you junk the PC.  Trust me, Ive been working with Macs lately and they wont make you feel any better.  The grass is always greener.

Note that OP has that problem at least once per 2 years:
http://forum.cakewalk.com/FindPost/3341078

 
 

azslow3
Note that OP has that problem at least once per 2 years:
http://forum.cakewalk.com/FindPost/3341078

 
 

Good eye, Azslow

MelodicJimmy
Ugh. ...
...
Macs are looking better every day.....

Your post caught my eye because I just got back from helping a church *downgrade* from High Sierra to ElCapitan.
 
The problem was that the High Sierra installation broke the macOS Core Audio in a way that caused their otherwise perfectly reliable Behringer X32 to output grainy distorted audio that got progressively worse over 10 minutes to be completely unintelligible. 
 
It's a part of a larger cautionary tale that needs to be well understood.  Apple updates have forced me to change my choice of video cards in my Mac Pro, and have forced me to choose between running the latest fixed release of Final Cut Pro X in ElCap/Sierra versus the perfectly fine Adobe Creative Suite 5.5 (fully paid, no monthly cost) that won't run in the most recent macOS flavors.  
 
In contrast, my Sonar Platinum is humming along in Win7 Pro just fine in the same Mac Pro, and I'm experimenting with Win10 Pro in the same machine because DaVinci Resolve 14 isn't fully supported in Win7.  I'm doing this migration because it's annoying to change operating systems just for late-breaking edits to audio for the video.  Keeping both Sonar Platinum and DaVinci Resolve 14 in Win10 would be ideal, and I'm working to get there.
 
The pitch symptom you're experiencing certainly sounds like something at 48K is being played by the hardware at 44.1K (or worse, something at 44.1K is playing at 32K).  Either way, it seems to be a system sounds setting is sneaking in to override the Sonar-requested sampling rate of the audio hardware. 
 
The sunshine and roses days of 'Apple is better' are definitely in the rear view mirror. 
 
 

I'll put my money on typically M audio writes cr@ppy drivers... Been there done that. 
 
My spare backup DAW just updated last night to 1709 and I didn't have one thing change at all. Opened Sonar and went right to work, including AD2. I think it was 1703 was bad news myself. 

Yes, check that the project and your interface agree on the sample rate.