tr-626-rhythm-decomposer

Stock Features

Roland’s TR-626 Rhythm Composer is a nice little 16-bit drum machine and sequencer package with 32 tunable sounds. It’s got an easy to read sequence display, multiple outputs and external drum triggers in the back and pretty decent MIDI capabilites. Like all of the late model TR’s, the sounds are quite “safe”, but it’s a bending beast.
Check out some more info about the 626 here.

My Modifications

The sidecar I’ve added holds all the bends and modifications I’ve made, nearly 100 in all-

Distortions, Pitchshifting, mutes, kit changes, delay and flams, additonal metronome LED and LCD, and a very cool synth tone section with it’s own output are each dialed in with the switches and rotary knobs. Several bends can be combined at once for endless new sounds.
About the synth section, each drum sound now has a synth sound to it as well. Like the drums, the synth can be fine tuned by a few notes in the 626’s menu and ive added a coarse adjustment knob to go from high to low pitch quickly. With some work, the Rhythm Decomposer can be programmed to play a bassline syncopated with the drums.
mothership

Sound Samples:

(mp3)tr-626 rhythm (de)composer demo
The only instrument you hear in this sample is the 626 rhythm decomposer, a short sequence mixed live with a bit of reverb punched in.

(mp3) tr-626 rhythm (de)composer demo2
Again, just the 626, a single 2 measure loop, being mixed live. You’ll hear the original stock drum sounds followed by the mod/effected ones as combinations of bends are added to the sequence live. The 626’s synth output is being filtered externally too.

You can do it!

Though Roland may have originally designed these machines to do no more than back up crappy cover bands, they all have so much potential! I’ve probably only scratched the surface with mine. Areas to explore yet are individual pitch controls and rom replacement. There’s so many sounds locked in there, its our duty to set them free! If you’re going to perform brain surgery on your drum machines, you should make sure you get the most out of it. The amount of bends can be staggering, so I took my time documenting every possible straight pin-to-pin connection on the TR-626’s 32 pin IC15 (chip 8735KY). I thought plotting each intersection on a grid might be a good way to keep everything in order. I found that while most bends were unique, they were similar enough to group in to a few categories using different colors to represent them.

Bend Chart Color Key for TR-626’s IC15.
Drum kit changers: Drum sounds are replaced with other ones in the kit, good for instant pattern variations.
Flams, Echoes & Ring mods: Drum hits double, sometimes closely (flams), sometimes further (echoes).
Pitch shifting & Flanges: Tight flanges create a ‘pitch shifting’ type quality, drum pitches go up or down.
Static & Noise: Static or white noise gets added to the sound.
Envelope gating: Envelope is clipped short, quick decay.
Distortion: Add your favorite flavors: Crunchy, noisy and/or overdriven.
Synth tones: Square wave sounding tones are added to the output.
Drum mutes: Mutes one or more drums.
X = Causes a crash.- Avoid this.
• = These are Burnkit2600 favorites!

01
02
03
04
05				•
06				•	•
07
08					•
09
10
11
12		•	•		•				•
13
14
15
16		•	•
17					•
18
19
20												•
21				•		•				•	•	•				•		•		•
22				•						•								•
23									•					•
24					•
25									•
26		•						•	•			•									•
27								•										•
28		•			•
29		•														•
30																•
31
32		•							•							X						•			•			•	•	•
pin	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31

So,
to clarify what you’re looking at…
In the bottom left corner of the graph there is a ‘teal’ colored box with a dot in it. The color signifies that it’s a kit changing bend, the dot tells you it’s one of my favorites. To add this mod to your 626, look at the corresponding numbers around that space and connect those pins of IC15 together, in this case it’s pin 32 and pin 2. Reading the numbers on the left first, then below the graph, 19 & 13 is a distortion bend; 4 and 2 is a ring mod, and 32 and 16 is the one crash I found on this chip.

Hear the same pattern with different mods: (mp3)zone 1 synths (mp3)zone 2 distortions (mp3)zone 3 flanges (mp3)zone 4 kit swap (mp3)zone 5 flams (mp3)zone 6 black box combo

Now with all these bending options, deciding what to keep and finding room for all the hardware may be the hardest task. I used a breakout box to house all my switches and knobs, running a flat cable to it via a slit I made under the 626’s cartridge port. Here’s the breakout box lay out: 1) 6 position rotary selects a synth sound, the switch routes the signal through the main or the synth output. 2) 12 position rotary used in series with switch selects 24 different distortions. 2nd switch momentarily connects. 3) 18 position rotary switch (with oven dial) selects 18 different flange effects. The switch turns this on/off. 4) 6 position rotary in series with switch selects 11 kit changing mods and 1 full mute. 2nd switch connects momentarily. 5) 6 pos. rotary in series with switch selects 12 flam and echo effects; 2nd switch selects 12 ring mod effects. 6) The black box area on the panel houses 3 momentary-on buttons, 1st mutes all but the synth tone, 2nd engages the selected kit change, 3rd engages the selected flange. Middle toggle switch disengages the synth tone to cut back on noise when not needed. Yellow LED pulses with the metronome. -Since these bends can all be turned on independently, there is a mind-boggling number of combinations possible.

TR-626 Rom Hacking!
Folks have always talked about replacing the sound roms of the Roland TR series with new samples.
On the Yahoo TR-707 groups, readers were able to combine both the 707 and 727 sounds into one machine. But, it was generally thought of to be impossible to bring new samples into it, but Gordonjcp proved them wrong! Deconstructing the roms in a fashion similar to Justin’s HR-16 sample replacement work, Gordonjcp pulled the 626 rom chip out, read them with his EPROM programmer, unscrambled Roland’s unusual sample format, swapped in new sounds, burned them to a new ROM and popped it in to his 626.
Viola, new samples! drums.mp3
Though his 626 eventually died an untimely death, Gordon proved it was possible and opened the door for other would be Roland rom hackers. If you’d like to attempt this awe-inspiring D.I.Y. task, you can follow his progress below in our comments #76 through #108 and check out GordonJCP’s site for more info.

Check out how some other folks bent their 626’s using our info
& send us photos of yours!:

from adam

from alan

from Heitor.

	from Pasha (mp3) (mp3) (mp3)

	from Poumtaq (mp3) (mp3) (mp3)

from George Gleixner George’s beautifully recased modular 626 features several great mods not listed above, including individual drum volumes/mutes, instantaneous fills and more. Until I figure out the best way to post this info, see the Word document linked below that he sent me for a description of how his patch bay is set up, and instructions on how to pull off these great mods. (word doc) (mp3) (mp3)

from Tobias.

But that’s not all! Because all of the mods I’ve listed only cover IC15, there’s plenty of uncharted territory throughout the rest of the circuits. If you find some interesting new things, go ahead and comment below or email me and together we can continue to exploit every last bit of this drum machine. See the comments below for a few extra bends and discussion of the 626 pitch modifications.
If you’ve read through this and if you’re up to the challenge feel free to comment in our forum with questions, comments, or more useful modifications you’ve found. Don’t take us for granted though, if you use this info, please give us the proper credit in a link and a shout out or send us a picture.
If you feel that you’re not up to the challenge of bending your TR-626 or other devices, let me do it for you! Contact me for options and pricing and such.