soundsc() cannot be stopped.
To play a sound at the maximum possible amplitude like soundsc does, you should use
centered_x = x - repmat(mean(x), size(x,1), 1);
maxx = max(abs(centered_x(:));
scaled_centered_x = centered_x ./ maxx;
Now you can use audioplayer's play() method on scaled_centered_x .
Note that when you are building an equalizer, you do not want your sound to be continually readjusting its volume. Suppose, for example that one of the performers is tuning their guitar: you do not want the tuning plucks to be automatically full volume. You should only be doing this kind of automatic scaling on completed sounds that have the entire dynamic range represented.
