The Messenger is Bruce Gordon's first Spectrum interface for over 2 years, but it seems that the old man hasn't lost his touch on producing a fine piece of valuable hardware for any SAM-Spectrum owner.
The Messenger is a black box which hugs onto the Spectrum's edge connector, and has a cable linking to the Coupe's MIDI ports. From here, you can load up Spectrum stuff on your Spectrum, then once the game is loaded, "port" the code across to the SAM. A button on the Messenger itself freezes the action of the Spectrum - a lot like a Multiface, and with this, you can do the business and save it to disk.
Because you are loading stuff on the Spectrum itself, there is a very, very high compatibility rate of 99%. The other 1%, I think, is for a crap tape header, or something. There's no buggering around with tape volume at all, and it's all extremely friendly to use. In short, a worthwhile and essential purchase for any Spectrum-SAM owner!