Hey what is the purpose of the overload light? Is it bad when it goes on?
It’s an overload light, when it comes on the sound is too fat.
Just kidding. It’s a clipping indicator when using external audio. Clipping won’t damage it, but it does neat things to the sound.
Is it ever a “good” thing when the light comes on. I was told if I plug the low out put back in to the loudness input and then adjust the input until the light flickers on the attack is a good track for getting punchy bass. Is this true?
Personally I don’t put much belief into the out-to-in trick.
Others will argue they found nirvana. Whatever. It’s subjective.
Jan Hammer one mentioned he used it sometimes and the gospel began.
A few things tho:
Sending the audio out back into the input can lower resonance (emphasis) settings.
It’s normal for the light to briefly flash when a Mini is first turned on and sometimes when it’s turned off.
If your light stays on continuously with nothing plugged into the input, something is wrong usually.
So if one fuse or the other blows, often the light comes on.
In this way, it acts as an “error lamp” indicating a blown fuse or something else wrong.
Another bit of info that I didn’t know about. Thanks Kevin.
Although at 1/4 amps slo blow for the -10 VDC and 1/2 amps slo blow for the +10 VDC, I doubt that any of those two fuses will ever blow, unless something is dangerously wrong inside the Mini. 
As for the out-into-ext in trick, I use it mainly for lead type sounds, as an “overdrive” effect. For bass, I feel it’s too distorted and, as Kevin mentioned, it reduced the resonance level of the filter.
It doesn’t add fatness. It adds distortion. And it’s not a trick. I totally agree with Kevin.
Marc, if it’s not a trick, what would you call it then ?
I’d call it a feedback patch, not a trick.
My understanding of the term “trick”, in this case, is a way to have something done that was not foreseen by the instrument designers.
It is technically a “patch routing”, but the result is a well known “trick of the trade” instead of using an external overdrive or distortion effect.
It has often been copied and already integrated by other synth manufacturers in their products, with some variations on the theme, later on. MFB Kraftzwerg, Arturia Minibrute, Moog Sub Phatty come to mind.
The Sub Phatty does not have a built in feedback path, though you can use the headphones into the External In to accomplish that. It does have Multidrive which is a distortion circuit that is quite nice. Also, you can push the mixer to overdrive. The Minibrute’s Brute Factor is in fact an in-built feedback path. Don’t know about the MFB but other synths that come to mind are some in the DSI line like the Mopho and the Evolver.
What do you think the MultiDrive knob does on the Sub Phatty ? 
Well, it doesn’t feed back the audio path it’s a distortion circuit.
And what do you think results in feeding back the audio signal into the external input ? Distortion. 
And feedback of audio is a crucial technique for distortion circuits
The Sub Phatty does not have a built in feedback path, though you can use the headphones into the External In to accomplish that.
The Multidrive is an OTA and FET circuit that’s actually very clever - dialing in a little give a nice FET warm overdrive and dialing in a lot brings in the OTA’s to breath their particular fire.
Another “trick” you can do with the overload light is use it to silently tune your oscillators together. By patching in the headphone output to the external input. You can switch off the main output, and by carefully adjusting the overload light via the ext. volume, you can see any two oscillators beat rate against each other.
Fellow list member Kenny Fine demonstrated that trick for me at Vibronic Music back in the summer of 1974. Always found that handy in certain live situations.
Feedback loops are what makes many modular patches interesting. Within a modular you can put this loop anywhere, and even control the ammount through a VCA, via any CV source. Right now my favorite seems to be a feedback loop with the 904B highpass filter. Just taking a little bit of the 904B output looped back into a CP3 mixer gives an incredible ammount of possible tones.
Here is a demo of just how different the tone is when a feedback loop is used with the Moog 904B filter. For the first 8 seconds a normal Moog tone of three 901 oscillators and a bit of 903 white noise. At 9 seconds I patch the output of the 904B back into the CP3 mixer feeding the 904 filter combo. The noise source becomes much more noticable, along with a bit of that Moog transistor distortion. A beautiful thing, that Moog tone!
Small 27 second demo of Moog 904B feedback loop 1.1MEG MP3 download
Those feedback loops do something very different to the quality of the tone. Another color for your sound pallet.
That’s true. It lights because the intermodulation of the two VCOs increase the amplitude when they cross.
Rivera Music Systems used to mod some Minis with an improved circuit and a separate LED.
Looked a bit ugly to me, but as you said, it could be very useful live.
Had they included a (divided-down?) A440 signal, they could even have had an absolute pitch reference.
The trick above (and RMS’s) could both tune oscillators together, but they could both still be out of tune with true pitch.
Agreed. Resonance (emphasis) is really nothing more than feedback.
Usually it’s inverted 180 degrees, but it’s still feedback.
Feedback on a 904B is certainly not a subtle effect though.
Things can get really wild or screechy depending on the patch.
Still, I think it’s a pity to own something as variable as a Moog modular, then set it up like a big Minimoog or other standard synth “voice.”
It’s a modular- there’s rules to be broken!! 
The Polymoog had a BEAT LED under the tuning pot that was simply an XOR with square waves from both HFOs.
[quote=“CZ Rider”]
Feedback loops are what makes many modular patches interesting.
[/quote]Agreed. Resonance (emphasis) is really nothing more than feedback.
Usually it’s inverted 180 degrees, but it’s still feedback.
Feedback on a 904B is certainly not a subtle effect though.
Things can get really wild or screechy depending on the patch.
Still, I think it’s a pity to own something as variable as a Moog modular, then set it up like a big Minimoog or other standard synth “voice.”
It’s a modular- there’s rules to be broken!! >
Well, the Minimoog architecture was derived because that was the popular routing on the modular in the RA Moog studio.
Heck, Keith’s modular is essentially the same routing of the minimoog, with extensive modulation capabilities 
Habits are hard to break… and then there’s Buchla 
I give a pass to Keith. He’s an exceptional player.
Given his talent, he could play a cheap Casio and probably provide more musical entertainment than most of us.
He also has a certain amount of constraints present when using a big modular live.
Yep and playing with a Buchla (and to some degree, a Serge) is just the tool to break such habits.
Their method of multing by stacking patchcords lends itself to trying things one might never do on a standard modular.
Their range of control also exceeds many standard modulars.
You can take the same module and patch it as an LFO or a crude env generator. With enough of them and a sample and hold, a sequencer,
They don’t always define modules specifically as one function, so it changes a person’s approach to patching.
I like that sort of environment.
As an opposite example, on a Korg MS-20, they have a pitch to voltage converter built in.
But insert one patchcord and it can turn into an LFO by feeding an output back to the input.
CZ, have you ever tried adding feedback to a 907 or 914?
That can make for some interesting effects.
Both positive and negative feedback can yield some crazier-than-normal sounds.
For somebody using a modular live in a non-Minimoog way, check out Robert Rich. Awesome ambient music, and he also helped Paul Schreiber design some of the MOTM modules. And he’s a great guy! http://www.youtube.com/watch?v=z0qQYFA0dUg for example.