Works perfectly thanks!
Seems there is a magic number though as I hit CTRL+F12 too many times the sound starts to lag...
Weird - Anyways hit the magic number and it runs smooth as a baby's bottom (that was a weird thing to say :P)
I don't quite understand how you would do this on the mac though, the f12 is just the volume button on my keyboard so I just raise the volume if i CTRL + F12. Any ideas?
You need to press the Fn key as well, this switches the behaviour of the top keys to F1, F2 etc. keys.
You can also change the default amount of cycles DOSBox uses if you right-click Dungeon Keeper Gold.app in your Applications folder, and choose Show Package Contents. Browse to Contents/Resources, and then show the package contents of the file named 'Dungeon Keeper.boxer'. Open the DOSBox Preferences file in there with a text editor, and change 'cycles=...' to 'cycles=fixed 100000', or any number of cycles you want.
I changed it to cycles=max, but I have an older Macbook and when I zoom out in high resolution mode (with ctrl+arrow down) it still lags a little bit. There's probably no solution to this, since it's just the limit of what the processor in my Macbook can handle.