To block a host: Tools>Options>Filters>Hosts & then add each one individually & press the Apply button.

If host is unavailable, it means they may be away from their comp (many people leave their comp on overnight or whilst they're at work/school.) Or they have the program hidden in the background whilst they work on other applications. OR they've decided they don't wish to chat. Just b/c you get that message doesn't mean they've deliberately snubbed you! So I hope you'e not going to block them for just that reason. You'll find you get that message quite often. If you block them & they were unaware of your message, then that's not really fair on them.

I don't know about music hall, but it could be a rip off version. Perhaps somebody else knows.