The difficulty scale is equivalent to the present time of DDR starting in which the latest extension for DDR started with DDR X. This extended to Level 20 for Sound Voltex IV. It opened a bigger opportunity for the experts but for me, the change doesn’t affect me that much as I’m still attempting the remaining Level 13 songs from Sound Voltex Booth and III. Level 14 onwards is already more difficult enough for me like I managed to clear some.
Another change was that the song unlock feature was made less difficult and you can unlock the songs at anytime in the music select screen. One condition is that certain songs can be like accessible in the final stage or something. Elsewhere, you still need the sufficient amount of blocks to unlock the songs.
The Music Select and Entry BGMs are what I can think of mashing up with and especially for the Matching screen BGM. Strangely enough, there’s no Title Screen BGM whatsoever.
There’s also the new type of FX note that causes the clap sound or any other sound depending on the song when you press it correspondingly. Unfortunately, I don’t like the way some parts of the notechart are set up for certain songs like the patterns are akin to doing the disgusting calls and responses as gross nerds do in concerts. It has been like this ever since the first Sound Voltex game with some of the Exit Tunes songs and the notecharters/effectors of those songs can go fuck themselves. Even the theme song of Sound Voltex IV, Heavenly Smile, is guilty of that bullshit for sure.
A recent update included the Skill Analyzer except that it is part of the Music Selection screen that you have to open the folder list and go to the Skill Analyer folder yourself.