More details:
If the difficulty stars identify the map as Easy, only 3 buttons are used.
If the difficulty stars identify the map as Normal, 4 buttons are used.
If the difficulty stars identify the map as Hard or higher, all 5 buttons are used.
Hitsounds would translate to multiple button patterns as follows:
Normal: *
Whistle: *..*
Finish: **
Clap: *.*
WF: ***
WC: **.*
FC: *.**
WFC: ****
These patterns are moved left/right (and possibly wrap?) according to the object placement rules:
For objects with New Combo markers, their column placement is chosen in absolute screen terms.
For all other objects, their column placement is decided relative to the placement (and distance) of the previous object.
In both cases, up/right correspond to placement further right and down/left correspond to placement further left.
When moving left, WhistleClap and FinishClap patterns are reversed to preserve symmetry.
The hitsound patterns will be changed for Easy to fit within 3 buttons and not overuse multiples.