the delay works good: the other 3 do nothing
We're making progress. Slowly. Which pin is the delay connected to?
but if i remove the slide key with an LED at the end and shine a flashlight directly on the photoresistor, it does start to work
You seem to be very familiar with the hardware and music side of the device. I am not. You seem to be barely aware of the programming side. That is my area of expertise. If you could phrase your answers in terms of "the thing connected to pin n", I will have an easier time following.
So, what is a slide key, and why do you need to remove it to shine a flashlight on the photoresistor? Where should the light on the photoresistor be coming from?
that is why I deduced that the variables need adjustment - the output range is too low.
It could be that the input range is too large, instead. If the actual voltage that the pin sees varies from 0.1V to 0.25V, and you tell the map function that the range is from 0 to 500, that does not correlate well to the actual range of values seen.
could you tell me what analog offset is? it must be a valid command, because the compiler did not reject it
analogNoffset is not a command/function. It is the name of a variable that stores a value.
question is, which direction should i change the variables? if i knew which variables to change, it wouldn't take long with experimentation to get it right. ( the actual output is measured in mv, not ohms, because there is an op amp feeding the photoresistors in series with the Arduino, so the ohms fluctuation alters the voltage output).
You are reading the values of the various pins in setup(). Printing the values that you read to the serial monitor would give you an idea of the initial values.
On each pass through loop(), you read, constrain, and map all in one statement. Break those into three statements, and print out the values read from the analog pins, the constrained value, and the mapped value, for each pin.
It should become fairly obvious what the problem is, quickly.