most of the horns are of "drinking Horns": and this one at the British Museum seems a bit large, it is because it comes from the now extinct auroch:(which is sort of a huge version of a Texas Longhorn).
And although there are lots of reports of the Vikings using such horns, I can't find much about their use in the AngloSaxon times, although they were indeed in use for making noise.
So what did they sound like?
The instrument most people think of in connection with the Vikings is the blasting horn or trumpet (O.E. blaedhorn, blaeshorn, bleme, horn, sarga). This instrument was certainly used by both Viking and Saxon, although not just for music - it was used when hunting and on the battlefield too. Usually these would be of ox or goat horn, although wooden examples are known. Many horns were decorated with cast or incised metal mounts. A few of the horns actually had finger holes cut in them in order to play tunes on them, although this is not really necessary as a skilled horn player can play a tune on a horn with no finger holes.