The method isRunning is added

[prko]

There is no way to know if the spectrogram is active or not. Thus, I added the method isRunning.
It works!

s.boot;
w = Window.new("testing spectrogram", Rect(10,10, 600, 300)).front;
a = Spectrogram.new(w, Rect(10, 10, 580, 280));
a.start;
a.isRunning // true
a.stop
a.isRunning // false

[JordanHendersonMusic]

Why not just add the read accessor '<' to the variable running in line 11? This could probably be renamed to isRunning for clarity.

(Just a comment, not a proper review)

[prko]

Why not just add the read accessor '<' to the variable running in line 11? This could probably be renamed to isRunning for clarity.

(Just a comment, not a proper review)

running is used several times throughout the code. I thought isRunning was a common way to do it, so I did it. However, your suggestion is the simplest implementation!