2019 Mac Pro no startup chime.

The initial "chime" sound is generated in software when your Mac passes the Power-On Self Test. If it occurs and/or startup continues, your Mac is working. In your case it may be muted or disabled.

The solid Apple is not in the Mac's ROM at Cold start. The Apple logo can only appear when it is fetched in the first "blob" of software loaded from a 'magic' place on the boot drive, or re-run after a Restart. Then a whole lot of stuff is initialized, and the progress Bar moves part way across. After a cold start, seeing the solid Apple appear says your drive is not completely dead.

The next step requires a lot of files by name, so the File System is initialized, and the Boot Drive is Mounted. If the drive directory is damaged, the drive can not be Mounted, so your Mac begins one pass of Disk Utility Repair. This will take an additional about five minutes. During this process, the progress bar may be extended, and will grow by an additional amount not seen on a routine startup.

at the end of that process (which should not take more than about five minutes), it will attempt to Mount the drive again:

-- if the drive Mounts, boot-up continues.

-- if the drive cannot be Mounted, your Mac can do nothing more, so it powers off.

-- if the process stalls, this may indicate you have Bad Blocks on your Boot drive. The re-reading of Bad blocks can take a very long time (on the order of a quarter minute for each Bad Block).

Well, I've heard it once or twice now, but I'll be ****** if I can get it back (I cannot). At least, not after installing Boot Camp (have not tried rebooting into Windows yet. That's a whole different drama b/c I couldn't run sysprep on the old one).

I have tried disconnecting everything plus power cable, waited well over a minute to reset the SMC (or whatever it's called) controller, reset the parameter RAM (Cmd+Opt+P+R), disconnected everything but the keyboard and tried resetting PRAM again... etc., etc.

I'm using the old "snack tray" keyboard (model no. A1048), if that matters. Also needed 3 Thunderbolt 3 to TB2 adapters (1 for my Thunderbolt Display, plus 2 TB2 RAIDs).

I would tend to think it's more something with the UEFI and not peripherals or Boot Camp. Like I said, I unplugged all of them while trying everything, and the chime was spotty at best before Boot Camp was installed.

And solid power button the whole time through the process except when it was powered off. It showed the apple logo 2x each time, also. AND it reset my Startup disk control panel to no disk selected each time I reset the PRAM, so that is doing *something* at least...

Every new model from Apple has a firmware update it seems so maybe in a few weeks they'll figure it out.

The trend has been toward removing the startup chime.

Any signs of life? any blinking power button?

This third-party article may add something:

https://www.macobserver.com/tips/quick-tip/reenable-macbook-pro-startup-chime/