Register

Samantha used this wonderful word in her analysis of the business letter. Here are two meanings from my computer's dictionary:

• a particular part of the range of a voice or instrument : his voice moved up a register | she plays a basset horn and relishes the duskiness of its lower register.

• Linguistics a variety of a language or a level of usage, as determined by degree of formality and choice of vocabulary, pronunciation, and syntax, according to the communicative purpose, social context, and social status of the user.

Register in the context she created no doubt means the second, but I like the idea of it suggesting both: the voice on the page striking the ear of the reader in a way determined by language use.