Composers' revisions really fall into two main groups (though each group itself can be sub-divided many times over). The first group I should name ‘practical’, i.e., revisions or after-thoughts which are designed to make a work more viable; we constantly meet this kind of revising in the opera house, but I should also include under this heading those cases where a composer has written, say, a complete new movement to replace an existing one. More often than not, this is the revision of an early work; his intention is ‘practical’—to get rid of the one, perhaps feeble, movement that goes against the chances of the work's success and thus save what is worth preserving in the rest of the work. This is what we might call good husbandry on the part of the composer. He keeps his crops, so to speak, in the best and most marketable condition.