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This page is read from MIDI Instrument Definitions, a Python library used in the author's other projects, in which every number is traced to a document its maker published. Its source is on GitHub.

Roland TR-909 MIDI implementation

The MIDI implementation of the Roland TR-909: what it answers to.

At a glance

Firmware
Not recorded.
MIDI channel
Any one of 1 to 16.
MIDI mode
Receives in 1 (omni on, poly) and sends in 3 (omni off, poly).
Voices
Not recorded.
Notes
Each note plays a drum of its own. Which note plays which is not recorded.
Note range
35 to 51: B1 to D#3, counting middle C as C4.
Velocity
Sent and received. Release velocity is ignored.
Aftertouch
None, sent or answered.
Pitch bend
Not recorded.
Program change
Not received or sent.
MIDI clock
Sent and received.
Start and stop
Sent and received.
Control change
None.
NRPN
None.
System exclusive
Supported.

Where these facts come from

Source documents

How they were read

The TR-909 Owner's Manual, 43 sheets, which is the only document Roland publishes for this instrument - and Roland's own manual archive, which is cited for that being true rather than merely unfound.

THE MANUAL IS A SCAN AND HAS NO TEXT LAYER AT ALL. 43 sheets, one image to a sheet, no fonts and no drawings - so every word quoted here was read off a rendered page by eye, and the quotation checker reports them as unchecked rather than as wrong. That is this corpus's established position for a manual of this age and not a new liberty: roland/juno_106, roland/d_50, yamaha/dx7 and korg/m1 are all built from scans the same way, and the library holds eight such files. The archive page beside it is text, so the claims that rest on it are checked in the ordinary way.

ITS MIDI IS THREE PAGES OF PROSE AND, FOUR SHEETS AFTER THE LAST, A CHART. See the comment above the definition. The chart crosses Control Change in both columns, so this is a definition with no controls on the maker's own word. The chart was read twice, by two readers who did not see each other's reading, each from a render of its sheet made with a different program, and the two agree in every one of its 26 rows. The second reader found the sync chapter's MIDI and the External Instrument Mode, which the first reading had not opened.

THE PAGE OFFSET IS +1 AND IS WORTH STATING. The scan opens with a cover, a contents sheet and a panel sheet twice the width of the others, none with a folio. Counting the wide sheet as two pages is what puts printed 5 on the fourth sheet, where it is, so printed page = sheet + 1 from there on. The second reader read every folio from printed 5 on the fourth sheet to printed 41 on the fortieth, with no gap. Printed 38 is the MIDI page and printed 39 the specifications. The chart's sheet, the 41st, carries no folio either; by the same offset it is p. 42, and it is cited so.

A FIGURE IS GIVEN TWICE AND DIFFERS. The trigger output is "a positive 14V, 18ms" (manual p. 38) on the MIDI page and "+14V, 20 ms pulse" (manual p. 39) in the specifications, a page on. Neither is a MIDI message - it is a jack that pulses with the rim shot - and it is recorded because it is a place where two pages of this manual can be checked against each other, and they disagree. The receiving channel at power-on is another, set out above the definition.

HOW THE DOCUMENT WAS FOUND, WHICH IS NOT WHERE THIS MAKER'S CURRENT ONES ARE. The global support page for this product, by_product/tr-909/owners_manuals/, is an empty shell: it builds its list in the browser and its markup carries no document link at all, where the same page for a current product carries nine. The archive page that does carry it is on the US site, which is where roland/juno_106 found its own manual two days before this. One guessed CDN address was tried and returned 403, which is evidence about the guess and not about the file; the address that works is the one the archive prints.

AND THE ARCHIVE IS SAVED ONCE FOR THIS MAKER RATHER THAN ONCE PER INSTRUMENT. The copy cited here is the one roland/juno_106 saved on 2026-10-02, and its visible text is byte for byte what a fetch returned four days later. The markup was not: two fetches of an unchanged page differ in four lines, a CSRF token and an ASP.NET view state, so the served bytes of this maker's pages are not a stable identifier while their rendered text is. That is a good reason to cite the text, which this corpus already does, and a bad reason to pin the HTML.

NOT RECORDED:

Its own specifications give the shape of the instrument - "48 Rhythm Patterns (16 x 3 Pattern Groups) x 2 (Bank I, II)" (manual p. 39) over four tracks in each of two banks, eleven sound sources, and MIDI sockets that are one IN and two OUTs - and none of that is a number this format holds.