You can edit the preferences to display 3 Spectrograms (Spectrogram, Melodic Range Spectrogram, Peak Frequency Spectrogram) under the Session template tab and then delete all but the hz Spectrum one and save as a template and you're good to go. I've saved mine and attached it for your use. hz_Rolling_Spectrogram.zip (931 Bytes)
Place this unzipped file in: C:\Users<i>yourusername\AppData\Local\sonic-visualiser\Sonic Visualiser\templates and restart the program. Then setup mp3tag to work with it in the options and voilà, Spek on juice.
To get fullscreen don't put the program full screen, just drag out the UI window handles to size, close & reopen the app. It should now remember the UI size until you resize it leaving out the \MAX bit in the parameter.
See attached screenshot to show how you can save the current window layout and set as the default:
Undeniably it has advantage over Spek and Spectro- it has a player function
Unfortunately I have some issues with it and / or that settings
1] It doesn't supports WV format 2] Sometimes files are loaded in a maximized way [stretched from left to right] and sometimes the are squished on the left side, requiring additional scrolling 3] It seems than smaller files [shorter than around 1:45] I have to zoom in or out, to show up any data 4] I can't make the maximized mode a permanent one, even when adding /MAX parameter in Mp3tag
I use on a daily basis MP3s, FLACs, WVs; so ability to see all of them on a spectrogram is a must. And it would a convenient if I could also analyze WAVs, because I often extract audio from video to that format, in which I later edit that audio [if it looks good enough on a spectrogram]
So far, Spek gives me the most efficient / visual form, for all of my formats. If only it could also play audio...
As for maximizing window, I don't know if I understand: I have to use a workaround? Because I shouldn't expect for the real maximize option to work [be remembered]; but instead of it I should "cheat" by making the window so big that it only looks like it is maximized but in reality is not? If yes, then it doesn't work for me. I have as 21:9 monitor, which gives me some issues of that kind with some older software. So when I reopen the Sonic Visualizer after maximizing it or fake maximizing, it shows itself in a 16:9 aspect ratio. And on top of that I have a thin Winamp bar always docked on top of my screen, that also sometimes generates some issues of that kind; and there is just no way I will be closing Winamp every time I need to quickly take a look at spectrogram
[Right now I'm testing some solution to the problem of Notepad not being able to remember to open itself always in a maximized way, so maybe something will come out of it]]