Sometimes is also good to see the audio signal and the best tools for this job are the Oscilloscopes and the Spectrum Analyser. I ofter use this in conjunction with my modular synth. This helps me understand what is happening to the sound while processing the sound.
The most important tool is the Oscilloscope. I use the plugin produced by Socalabs. it’s free for both Mac and Windows computers and works perfectly. Download it for free here. Socalabs has also a free Spectrum analyser. If your DAW doesn’t have one get this one too.