Making noise

I needed some noise, and whilst there are many ways to create noise of various colours, none of them quite met my need (I wanted '11' and the noise I got only went up to '10'!). Instead of exploring the available resources further, I decided to think about my ideal noise source...

In the past, I've been guilty of using the very predictable 'noise with LFO'd filtering' patches that are often used to make surf and train noises. In my defence, whilst some of the synths in question were obvious examples like a MiniMoog and 'white-top' ARP Odyssey, I've also done much the same on slightly more unusual examples like the Oberheim OB-1, Synton Syrinx, Korg PS-3300, even a Yamaha GX-1 (I also repaired it) and others. But enough of the past...

Adding a phaser and some panning and you get a pretty versatile surf, wind, rain generator. As with Comber V0.3, I had the intention to make some sort of complex multi-filter section, and maybe add this to the phaser in Comber.

But then I stumbled upon fffb~ in a quiet backwater of the Max Help pages, and I realised that with a bit of tweaking, it could make a pretty useful dynamic filter bank. The Max Help pages tauntingly say: 'This object is more efficient than using a number of reson~ objects, but for the sake of speed does not accept signals for parameter changes.'. Well that was it, it looked like I'd found my versatile filter and I just needed to find a way round the control limitation.

fffb~ is quite a monster of a filter. You get 8 resonant filters by default, but you can go up to 50 if you want to, and I decided that 16 was probably enough for a first attempt. You can control the centre frequency of the lowest frequency filter (F in the diagram above), and then the spacing between the other filters as you go along the frequency axis (I've called this 'Spread', S in the diagram above). The Q of the filters is global, but still a useful control, and the F, S and Q all duly got separate LFOs to control them. The individual Gains (G) of each filter can be set individually - so I used a conventional multi-slider controller for that. Although you can't drive everything directly with signals, you can update the parameters in real-time, and this has much the same effect.

The Q control has some problems at low values, and whilst the jerkiness that this produces in the output audio can surprise you the first time, it can also be used to provide exactly the sort of chaotic uncertainty that you get with wind sounds. There's a red indicator to warn you as you go into this mode.

The Spread control is best left near the middle (= '1') at first. This keeps the filter stable - and NOTE the 'Reset' button for when things get out of control!

Because two noise sources are better for doing wind and rain, or surf and wind, or rustling leaves and howling wind, then I doubled everything, and added LFO-modulated panning too (that's 8 LFOs in total). There are colour-coded White/Pink noise selection buttons as well.

The three LFOs provide lots of control over the filtering, and you can make lots of wind, rain and surf effects - use a phaser after it ini the chain for better surf sounds. I recommend that you use the excellent built-in 'Spectrum' display to see the output of the filter, and turn it off when you don't need it to save processing power. I've included the Spectrum display in the screenshot below as a 'serving suggestion'.

So that's the mundanely named 'Noise Generator mr 0v01'. As usual, you can download it for free from MaxForLive.com. Enjoy!

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Refined Combing...

Things don't always go the way you intend. I had an idea for a phaser effect that was driven from a filtered noise source, and the end result was something rather different. Here's the story...

'Phasers' are just comb filters where the notch frequencies are modulated up and down in frequency by an LFO. (My previous Comber effect was nothing more than a few of these in one place.)

The audible effect for typical 'vibrato/tremolo' LFO rates sounds a bit like detuned oscillators, and so can be used as a simple 'chorus' effect (there are other ways of doing chorus effects as well). At slow LFO rates then the effect is more like several resonant filters sweeping up and down, which is exactly what is going on!

But whilst sine wave shaped LFOs are all very nice, there are many other possible alternative waveforms, and repetition can get a bit boring. So my idea was to got most of the way to the opposite extreme from the pure predictability of a boring sine wave and use noise instead. Filtered noise seemed like the right thing, and so I envisaged an array of resonant high-pass, band-pass and low-pass filters, and perhaps some sort of neat GUI control to create a final 'noisy' modulation for the comb filter.

Unfortunately, the end result was not as interesting as I hoped. High-pass filtered noise just gave a rapid tremolo effect, and not a particularly nice or useful one. Band-pass filtered noise was still too busy. The only really useful noise was heavily low-pass filtered noise, containing exactly the sort of frequencies that you would use for tremolo, vibrato or a phaser! After a bit of experimentation, it turned out that I didn't need any conventional filtering at all, and that just a bit of sample averaging (OK, primitive filtering) produced nice random wobbling that sounded ok - but it wasn't anywhere near as impressive as I'd been hoping.

So I wondered if something combining the LFO and the noise was a better idea, and I added a DJ cross-fade type control to mix between the LFO sine wave and the noise waveform. This seemed to liven up the result and make it a bit more interesting and unpredictable...

But then I realised that I had an alternative source of variation, and so I added a second LFO to drive a Sample/Hold circuit that sampled the original sine wave LFO. Sample/Hold circuits have always fascinated me, right from the days when you put high-input impedance op-amps on Teflon PCBs with polycarbonate capacitors and used reed-relays as input sampling switches, all in the analogue quest for long-term voltage storage (and you still got droop over time!). In the digital domain, things are different (and you add imperfections if you want to model the real world) and so a quick bit of M4L'ing later, I had an LFO with sine waves for high sample rates, and repeated complex patterns for lower sample rates. (The S/H samples when the indicator lights up yellow, btw.)

The DJ slider became a 'Randomness' control, and I added a red indicator to provide visual feedback for when the 'Freq' and 'Depth' controls needed to be adjusted (up and down respectively), and Comber V0.3 was born! I hope you find it a more versatile and inspirational effect for your music. 

Comber V0.3 is available, as always, for download from MaxForLive.com.

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