It's only limits in the demo are that you can only do so many actions in one sitting. Basically, it counts your actions, and after 150 of them stops the program from making further ones. All you have to do is save you work where you are, close the program, and then open it back up and you get 150 more actions. When you are in Goldwave, under "Effects", go to "Filter", and pick parametric Equalizer. A parametric eq is like a regular equalizer, but instead of simply lowering or rasing frequency values, you can cut them out completely. Then, drop all your bass and treble out, and you have a low bandwidth sounding piece of audio. A few more tweaks with different effects and you can get just the sound you are lookin for. I think as one of the presets in the Parametric eq, there may already be one for Phone sounding audio.
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