I just wanted to share how the SCI Drumtraks creates the closed hihat (ch) sound from the sample that is actually an open hihat (oh).
The hihat chip in the Drumtraks is a single 2764 containing a whopping 8 kb of samples. Remember that electronics where much more expensive back then, and costs must be cut. One method was to use the same sample for the oh and cc. This was the case on the Linn LM-1, Oberheim DMX / DX, Drumtraks and probably a lot of other digital drum machines from this era.
The trick is to use the last part of the oh sample and add some envelopes to it. Below is the Drumtraks hihat chip loaded in Adobe Audition.
The red marker marks sample number 4096, which is exactly half of the total 8192 samples. It’s approximately here the ch starts. But, when recording the ch, it doesn’t look exactly like that. Take a look at the recorded audio below:
To make the ch fade out quickly, an envelope is added by the Drumtraks. If you don’t believe me, compare this image to the first one, the peaks are easy to identify.
What about the oh, does it only play until sample 4096? The answer is no, the oh plays the whole 8192 bytes. Take a look at the screenshot below:
The first part is the oh recorded from the Drumtraks. Last part is the data from the chip. As you can see, they are ‘identical’. This means that when the oh is played back from the Drumtraks, the whole sample is used.
Notice how different it sounds when processed by the Drumtraks, and that’s the reason for having a Drumtraks. 🙂