> I have some .TD9 files which are recordings from the Roland TD-9 Drum Computer. (...) Are they anything like MIDI ?

They likely use similar concepts as MIDI files. In the TD-9 manual, page 41 describes the "quick recording" maximum size as a number of notes (instead of a number of minutes), suggesting it records note data (not audio data). And in a message board post, a Roland product manager says the quick record performances "contain MIDI data":

Can recorded performances be saved as audio wave data to the memory stick for external processing?
"Quick Record" performances (drum parts played and recorded from pads) actually contain MIDI data, however they are saved to a USB flash drive in a proprietary TD-9 format.

> How many bytes is a timestamp for MIDI ?

In a MIDI file, delta times can be between 1 and 4 bytes. Information about the MIDI file format is available in the Specs section of this site. Get The Complete MIDI 1.0 Detailed Specification (PDF, log in required) and go to the section "Standard MIDI Files".

> Any help to figure out the grammar of a TD9's .seq file would be greatly appreciated

If you post an example SEQDxxx.TD9 file, I'd like to take a look.

I also found a thread on a German message board asking about the SEQD001.TD9 file format. It includes the following information from Roland Customer Support that the format is "mostly MIDI data, but not pure MIDI data":

German original: TD9 - aufgenommene Spielsequenz
English by Google Translate: TD9 - recorded play sequence

The QR data of the TD-9 are mainly MIDI data - but not pure MIDI data. For example, if you create a QR recording with an internal song, the file contains information such as "which song, which tempo, A-B repeat on / off". It is not a separate audio format recorded within the TD-9, but a sequence of MIDI data (= your play) + numerous additional information. If you are playing a QR recording, you can listen to it with a different kit. This makes it clear that such a file can not be converted into a WAV / MP3 audio format. [...] Friendly greetings / best regards Fabian Olk Customer Support

There is also a lot of information on this subject over here on the Vdrums forum.

Vdrum Forum discussion

Hmm, this thread is now over a year old. I suspect that OP has now moved on to other things?

That aside, this does draw attention to the use of midi data in other file formats.

Long, long ago, I had some Yamaha Disk Orchestra disks, with the score booklets as well. The disks contained a set of music files, to be played on the DOM (Disk Orchestra Module). They were labelled as NOT midi. They were in fact NOT midi. But when I looked inside the files, there was clearly a lot of real midi data there.

I got a Yamaha doc about the structure of the file (called ESEQ), and wrote a prog to read the data from the Yamaha file and write out a midi file. I had to create a table to convert the Yam instrument list to GM. I needed to do something similar for the percussion sounds, but that never happened.

I also had to tweak a few things manually, I seem to remember.

I was able to create some midi files, that did play, and sounded pretty much as they ought to (drums aside ?). But really too much trouble, so things got 'filed'. I was looking at the file just recently. Might have another look? Then again, life's starting to seem just too short!!

This TD9 thing might be all in the same boat?

Geoff