A single resistor biasing the base of a transistor will turn on some transistors but not other transistors, even if they have the same part number because transistors have a wide range of current gain.
Also, temperature affects transistors, heat turns them on and cold turns them off.
A transistor turns on gradually, not suddenly unless it is in a circuit that switches it on and off quickly at a certain voltage. The circuit is called a comparator.
An LM3914 IC has a voltage divider feeding 10 comparators and it is made to do what you want, making an LED voltmeter graph. Sorry, they are obsolete and are not made anymore.