We plug in the old Grundig amp, and connect it to two separate sets of speakers, switched on the amp with the buttons marked 'Speaker 1', and Speaker 2'.
The cabin pair (Speaker 1) is really cool, in my humble opinion. They are Grundig 'Audiorama' spheres, from the '70's, and are omni-directional, meaning that you get a different sound depending on how they are hung, because the sphere contains four separate drive units, each facing a different direction. The boat has brilliant natural acoustic properties from all the wood and cushions, and it's possible to crank up the volume to Number 11 without distortion. Excellent.
And now to the rear cabin.
My mate Mike gave me a pair of Cambridge Audio bookshelf speakers, which I originally had up on the bit behind the windscreen. But then I discovered they fitted perfectly in the voids at the back. Great! Except that whenever someone came on board and sat on the rear deck, their bums muffled the sound.
Recently I had a Eureka moment of inspiration, remembering an old Bose Acoustimas system that my sister Emma gave me and I'd been keeping in the garage for a rainy day. The rest of her system didn't work, but I thought I'd try connecting the Boses to the Cambridges, giving me separate bass down below and treble up above.
I put the Boses up behind the windscreen, and Hey Presto, what a result! Thanks Mike. Thanks Emma.
So there we have it. How to get music on a boat in three easy parts.