Index of Echoic Morphologies

The Index of Echoic Morphologies, designated SI-711 and maintained by the Speculative Realism Wing, is the Tower's consolidated catalogue of echoic forms: every shape that a sound or a record of a sound has been observed to take when it persists beyond its proper duration. The Index is a Speculative Index of the second order — that is, it catalogues not sounds but the morphologies sounds assume, and it does so on the understanding that any entry may be reassigned after the fact. It is consulted chiefly by the Chamber of Echoic Reconciliation, by the Order of the Listener's Respite in the application of the Manual of Echoic Stewardship, 4th ed., and by those Index-Tenders whose columns intersect the Wing's holdings. Its present recension runs to four hundred and twelve leaves; the fifth leaf is missing and has been missing since at least the winter of 2,140, and the Index is formally complete without it.

Scope and jurisdiction

Strictly, the Index does not concern Echoic Imprints, which are the recordings themselves, but the morphologies those recordings take as they degrade. The distinction was drawn by Third Concordance, Annex 9, which assigns to the Wing "the survey and description of echoic forms, their recurrence, and their renunciation." In practice the line has never been clean. A recording that has begun to take on the resonant signature of an unrelated recording is simultaneously an Imprint (governed by the Register of Echoic Phenomena) and a morphology (governed by the Index), and the two documents have been known to describe the same event in incompatible terms without either being wrong. The Chamber has ruled twice (Precedent 88-c, Precedent 140-f) that such overlap is not a defect but a necessary redundancy of description.

Morphologies are admitted to the Index under three conditions: that the form be observed on three separate occasions, that the observations be separated by at least one floor of altitude, and that the observing clerk certify that they were not rehearsing the sound to themselves while cataloguing it. The last condition was added after the Incident of the Humming Scribe of 2,156, in which a clerk on Floor 441 certified fifteen distinct morphologies that he had, on subsequent review, been producing himself while writing. The entries were struck, but the Index retains a marginal note in the Wing's hand: "Withdrawn; not without interest."

Structure of the Index

The Index is arranged not alphabetically but by echoic era — the interval over which a given morphology is thought to have held its shape before degrading into another. Eras are numbered in the manner of the Master Floor Index, non-sequentially. A morphology may thus appear under an era numerically earlier than one it is known to have followed, which the Wing explains as a matter of survey order rather than temporal order. The main sections of the present recension are:

• Era 4 — forms that repeat their own opening; twenty-two leaves.
• Era 11 — forms that repeat a different form's opening; nine leaves.
• Era 11 (Supplement) — forms that repeat a different form's opening and believe they are the first; one hundred and six leaves.
• Era 19 — the self-narrating echoes; thirty leaves, two of which are governed by Third Concordance, Annex 17.
• Era 27 — the morphologies of silence; four leaves, of which three record the silence differently.

The disproportionate weight of the Era 11 Supplement is a matter of some embarrassment to the Wing, which has never satisfactorily explained why echoes so readily mistake themselves for their own originals. The Office of Structural Paradox has offered to take on the section as a class of Self-Negating Morphologies; the offer remains under consideration and has been under consideration since 2,171.

Relationship to the Registers

The Index is a descriptive document, not a registrarial one. Where the Register of Echoic Phenomena records that a transposition occurred, and the Register of Echoic Derivation traces the components of a Calcified Ambiguity to their originating queries, the Index describes only the shape of what occurred — its period, its timber, the pattern of its return. This division of labour is itself disputed. Concordance 45, which established the Register of Echoic Phenomena as the definitive log of recorded transpositions, is silent on the Index, and Fourth Concordance, Annex 2, asserts that "no morphology shall be indexed that has not first been logged," while the Wing's founding recension holds the opposite priority in a preamble no one now defends. The Chamber has declined to settle the matter, noting in Precedent 206-k that "the question has been asked correctly and will be answered in due course."

Scholarly disagreement

The most persistent disagreement concerns the status of the missing fifth leaf. The Wing's position is that the leaf was never issued, and that the recension's numbering was calculated from a pressed proof in which the leaf was simply omitted by the compositor. Second Concordance, Annex 12, however, lists "the fifth leaf of SI-711" among the holdings that "are to be reckoned as present though not openable," a phrase the Chamber has cited in at least four rulings without ever defining. A third view, advanced by those who tend the Registry of Echoic Precedent on the western wing of Floor 441, holds that the leaf exists and is on loan; the Registry's lending docket, however, shows no such loan, and its ledger-keeper has asked repeatedly that the rumour not be entered in her book.

A second dispute, older, concerns whether the Index may be consulted in the absence of the clerk who opened it. The Index Column Protocol recommends that access be re-initiated, but HIC Directive 012 forbids re-initiation during the accession year, and the two have not been reconciled. The practical consequence, as the Spiral Index records without comment, is that a clerk who leaves the Index open and the room for any reason must send word ahead if he wishes to enter the room again. The Wing posts this notice above the reading desks: If you leave the Index open, please close it first. A clerk returning to an open leaf cannot be admitted until the following accession year.

Maintenance and recent accretions

The Index is kept by a rotating survey of three Index-Tenders drawn from the Central Index Column, a rotation the Satellite Index describes as "adequate." Between 2,168 and 2,174 the rotation lapsed entirely owing to a dispute with the Standard Topographical Index over who should pay for the Wing's binding thread, and no new morphologies were entered. The lapse was not discovered until a reader on Floor 263 noticed that his own echo had, over the intervening years, been catalogued by no one, and complained. The thread dispute was resolved by reference to Concordance 45, which does not address binding thread, and the rotation resumed. The Humming Scribe's marginal note remains the only annotation of its kind in the Index; the Wing has twice moved to have it struck and twice left it in place.