Friday, 13 December 2013

DIY square wave oscillator with Korg-style ring-modulator

Here's something I threw together today. It's a pair of very simple square wave oscillators based on two 555 timers and a couple of CD4013 dual flip-flop ICs. The "ring modulator" is actually a single XOR gate. Korg used a variation of this for the ring mod the MS-20 (they used NAND gates in an XOR configuration).

The prototype on the breadboard
It's possible to tap the raw 555 signal, as well as the output of the first flipflop. You can either route them straight to the audio output circuit or via the ring mod for a variety of different sounds. I'm going to build a switch matrix that lets me do that without needing to rewire the board. You can use the XOR circuit on its own as an effects processor, but if you're using anything other than square/pulse waves as inputs you'll need a comparator before the XOR gate.

Schematic (produced in Yenka)

The next step is to replace the 555s with a PWM circuit with independent frequency and duty cycle control. A sawtooth oscillator and a comparator might work, but I've never done anything like that before, so it should be interesting. I'm definitely going to use the XOR circuit again though, it sounds fantastic.

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Sunday, 22 September 2013

Adventures in iOS - Creating loops on the go

This is a monumental moment for me - my first post using my new iPad!

I've long resisted the mobile music making world, but I have to say I've become a bit of a convert over the last few days. The workflow is so very different from using a PC or a MAC, but that's not such a bad thing. Making music on an iPad reminds me of my earliest experiences making music. Instead of having one program that does everything, such as Logic or Reason, you have lots of little tools that work together.

The first bits and pieces to come out of my iPad are a collection of glitchy loops that I've created using a combination of Propellerhead's Figure and Yellofier by Boris Blank. Figure is a gesture-based looper that let's you create a three part loop of drums, bass and lead. The patches aren't editable, but they come from Reason's sound bank so they're pretty decent. I picked a few sounds I liked and then used Audiobus to link Figure to Yellofier. If you're unfamiliar with Audiobus then think of it as a virtual audio cable that goes between apps.

Once hooked up you can begin recording into Yellofier. There are two ways you can approach this: You can set up a loop in Figure and just record a chunk of it into Yellofier and play about with the slices, or you can set up your sequence in Figure so that you capture 8 individual sounds. If you go with the first method then you're likely to get unpredictable glitchy results - which is always awesome. However, if you're a bit of a control freak and want predictable, clean results then use the second. Have a look at the two screenshots below for a comparison of what each method looks like in Yellofier. It's pretty clear which one is which.

OnceL your sound is recorded in you can choose your slice points. Don't worry if the tail of each slice seems too long; Yellofier is a monophic sampler, so it'll cut the slice short if you have another slice playing straight after it.

The song editor is made up of individual cells of 16 steps, so you can create loops of 16 or 32 steps easily, or even longer if you want to You can also layer up to four channels at once, using two sets of recorded slices and the built in samples. In this example I've only used one channel at a time, because all I'm interested in is creating some loops for future use.

The different colours correspond to the different slices, and the different shapes are different effects y can apply. The shapes can be rotated to change the severity of the effect, and you can also pitch shift each step. The effects are all quite glitchy, so they add a lot of texture and harmonics.

After creating a loop I like I export the audio into an app called Audioshare, which is an all purpose audio file manager. It has Dropbox support, so it's easy to bring samples in and out of the cloud, and it also has a normaliser, so if you want a quick and dirty way of making your samples louder without altering the dynamic range then you can use that.

That's basically it, a quick and dirty overview of some techniques I've been using over the past few days. Feel free to download the loops I've created, the link is below.

Download loops (122 bpm, G major)
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Saturday, 9 March 2013

Happy Birthday Blue Monday

So a few days ago Blue Monday turned 30. It doesn't seem possible that something so modern sounding could be so old! Anyway, enjoy. Regular posts resume soon =]

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Monday, 28 January 2013

Max/MSP Autosave (Mac Only)

One major headache with Max is that it has no autosave feature. Another major headache with Max is that it's not always entirely stable. This is by no means a perfect workaround, but I found a script online that triggers the key shortcut for save (cmd+s) every two minutes, but only when the app is in focus (handy if you're switching between apps a lot).

Unzip and add it to your startup items, or open it each time you run Max.

Full credit goes to Paul at Axure for his original script, I just modified it so that instead of looking for Axure the script looks for Max.

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Thursday, 24 January 2013

Sci-fi soundscapes with the Korg MS-20

Behold! The beautiful Korg MS-20. This little beauty belongs to Teesside University's music technology department, where I am currently in third year of my BSc. Yesterday I took myself off to one of the studio control rooms and started experimenting with it. Up until that point all I'd really done with it was noodle about like a wannabe prog rocker (sans the cape), and I wanted to see just what it could do. I should point out that I get a little over excited at times in this post, so please forgive my miserable writing skills.

Unfortunately this is the only photo I took, because the whole session was spend playing with the synth.
I've developed a bit of an interest into the old BBC Radiophonics Workshop, and I wanted to see if I could create some classic Dr Who-inspired sound effects. The patch bay is an absolute godsend for that sort of thing, but even without it the synth has some delightful functions hard wired into the front panel.

Unlike the Minimoog, the MS-20 has only two oscillators, but it is by no means limited. Oscillator 1 has a fully adjustable pulse wave, and Oscillator 2 can function as a ring modulator. The timbral possibilities these make possible are mind blowing. Using the ring mod in conjunction with the pulse width control of oscillator 1 and the pitch control of oscillator 2 allow for some absolutely filthy lead sounds, and with some careful modulation you can turn said lead into a living, breathing monster.

Another difference between the MS-20 and the Minimoog is that the MS-20 has two resonant filters, one high pass and one low pass, each with a slope of 12dB/Octave. Having two cutoff frequencies to resonate and modulate means you effectively have two more sound sources. Having the high pass filter also gives you a bit more control over bass frequencies, which can get a bit unruly if you don't keep them in check, especially when using feedback loops.

The audio processing capabilities of this thing are unrivalled. Apart from the fact that it can convert audio to a pitch CV (if you know what you're doing) the filters are perfectly suited for processing external audio. You can also set up a feedback loop, as it has two outputs. Plugging the headphone amp into the external input jack gives you a delicious growly sound that you can record through the standard signal jack. Whack a couple of effects in there and you can process the feedback, creating all sorts of weird sounds.

This recording uses every trick I mentioned above and more. Audio was routed out of the synth, into The Echo in Reason, back into the synth and then recorded out of the main output jack. The only other processing was to add a slight ping-pong delay to give it a bit more width (you've gotta love fake stereo). This isn't really music, but anyone who enjoys Sci-Fi from the 60s and 70s will probably enjoy it. This was recorded in one take, and it's a bit rough, but I plan on adding to it at a later date.

Check back soon for more analogue goodness, as well as new adventures in Max.
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