Thanks,
@jaymonkey.
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For anyone else, the thing with the inaudible alert sounds turned out to be a wire on the front audio cable broken off from the connector. A bit of solder and squinting and some cursing fixed it. So audio seems to be working correctly with AppleALC using the "properties" method of setting layout-id to 1.
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I bought this m/b and cpu because they were on the recommended list and reasonably-priced. I was surprised at how much trial and error was needed, compared to an earlier build where literally all I did was follow the vanilla unibeast/multibeast instructions. I guess if I'd been installing 10.13, or had an external GPU, things would have been easier. And I'm grateful to all the people who've shared their knowledge that got me going.
So here's where I ended up, hope this can help others:
* F10 BIOS, all the recommended standard BIOS settings.
* During initial install I had to have the keyboard/mouse on the front usb ports, and the installer on the back. Got the crossed circle otherwise.
* Patience while the initial install repeatedly rebooted (three times?) and looked like it was making no progress.
* Clover r4862
* Kexts, first in EFI/Clover/kexts, ultimately added to /Library/Extensions:
AppleALC.kext
FakeSMC.kext (plus the HWSensors ones)
IntelMausiEthernet.kext
Lilu.kext
USBPorts.kext (created using Hackintool guide)
WhateverGreen.kext
XHCI-unsupported.kext
* Drivers added to EFI/CLOVER/drivers64UEFI:
ApfsDriverLoader-64.efi
AudioDxe-64.efi
DataHubDxe-64.efi
EmuVariableUefi-64.efi
FSInject-64.efi
OsxAptioFix3Drv-64.efi
SMCHelper-64.efi
VBoxHfs-64.efi
* The attached config.plist