ISO does not create light. It changes how the camera maps the captured signal into the recorded image. Raising ISO is often blamed for noise, but a photograph captured with too little light and brightened later can look equally noisy or worse. The central question is whether you can collect more light without sacrificing the required motion and depth of field.
In low light, decide what cannot change. If a musician’s movement must be sharp, shutter speed has a floor. If two faces must remain in focus, aperture has a limit. Once those creative requirements are set, raise ISO enough for a usable exposure. A technically noisy sharp photograph is usually more valuable than a clean blurred one.
Expose carefully around important highlights. Concert lights, street lamps and signs may clip, but the subject should not be buried simply to preserve every bulb. Use the histogram and highlight warnings while recognizing that the JPEG preview may show clipping before the raw file is exhausted.
Noise reduction trades texture for smoothness. Apply it at the final output size and inspect skin, hair, foliage and stars. Color noise usually tolerates stronger treatment than luminance noise. Avoid aggressive sharpening before noise reduction, because it emphasizes the very texture you intend to control.
Stability offers alternatives: brace against a wall, use a monopod, time the exposure between movements, or capture a supported static frame. But stabilization does not solve subject motion. Additional light may be appropriate when it is safe, permitted and respectful.
Practice exercise: photograph a detailed static scene at each full-stop ISO with exposure kept equivalent. Then photograph a moving subject in the same light, first holding ISO low and then allowing Auto ISO to preserve shutter speed. Compare at print or web output size, not only at 100 percent magnification.