Many thanks, Bob. BIOS boot works fine always, even the GRUB part works. It is the third part of the boot/startup sequence which hangs if booted while connected up. Anyway, I will try the mode without HDMI init to see what happens.
May I trouble you with another issue, that of gapless no longer being so with Volume Levelling on? I experience gaps between a fraction of a second to as long as 10 seconds, between gapless tracks, since I have turned Volume Levelling on on the MC server (Mac) while playing through Id. I think it is related to how long or complex the next track is, since the gap is longer when playing 5.1 track than when I play its otherwise identical 2 channel version. Also, longer tracks mean longer gaps. I run Activity Monitor on the server to see what's happening, and I can see that about 2 seconds before the tracks change MC gets busy, spinning the processor usage up, and the duration of the unwanted delay matches perfectly the moment when MC is done with its high CPU task. Longer multichannel tracks mean MC is using 100% CPU while simpler tracks peak at 60% on my 2009 Mac mini. Memory is no concern. MC seems to be using about 30 threads.
Is there a setting where I could force MC to perform the volume levelling operation earlier than the 2 s prior to when the file is needed? This would be a simple way of diagnosing and troubleshooting this issue at the same time. Ideally, the next track would be readied some 15-20 sec earlier. I realise this may mess up last-minute track changes, but the majority of the time it would enable gapless to work with Volume Levelling on less powerful (but still very capable) hardware.
If I am wrong, please set me right. Many thanks, as always.