A query about non-inverting op-amps

[ElectricDruid]

I've noticed recently that sometimes non-inverting op-amps have an "extra" resistor from the junction of the potential divider back to the inverting input. Can anyone tell me what this is for?

An example is the Boss DS-1, but there are a few others:

https://www.electrosmash.com/images/tech/ds1/boss-ds1-distortion-schematic-parts.jpg

I'm talking about R11/100K in this schematic. Without that, VR1+R13 make your standard non-inverting op-amp, like you see in text books. They've added a couple of caps for tone shaping, but I understand that bit. It's just that extra resistor back to the inverting input I don't get. What's it for?

Thanks!

[PRR]

Perhaps:

Opamps with significant input bias currents and large bias resistors will have DC offset errors. Equalizing the resistance to both inputs can reduce this. (Here, R11 et al compensates R39 et al)

Also large external signals can burn-up inputs; a resistor makes this harder to do.

But here I think it is just loose thinking. Older designers got in the habit of sprinkling resistors. But there's no external signal to the blue box section, and DC offset of tenths-Volt is unimportant.

[R.G.]

I've seen that trick used for lowering the apparent gain of the opamp. Some opamps are not compensated for unity gain, only gains of as low as five, or ten. I'll have to go look it up.

[anotherjim]

The data for the original DS-1 opamp specifically warns the inputs must not go negative of the supply. I think the designer got scared by this and added the reverse clamping diode with a series resistor to limit the current if the clamp ever operates. Since that input comes from a DC blocking capacitor, I suppose there is a slight risk of a charge-pump acting during power-up/down cycles producing an out of range voltage on that input.