XA CONTROL is a parameter found in normal Voice Elements. There are two types of Voices: drums and normal (sort of like there are two types of people: normal and drummers!!)

Normal Voices are for musical instruments, typically, and contain 8 Elements, that can be mapped both vertically (by velocity) and horizontally (across a note range).
Drum Kit Voices are for drum and percussion instruments, typically, and contain 73 Elements... That are mapped vertically to a single key.
That said, you can create specialty drum/percussion "kits" using the Normal Voice architecture, as found in the 8Z (or 8 zone Drum) Voices. Or you can simply use the 8 Element architecture to house several versions of the same sound.

For example, to make a ride cymbal (a constant staple of swinging jazz) more realistic, you could create a Voice that did wave random through several slightly differently tuned ride cymbals. Or that contained multiple crash cymbals so that they randomly change as you use them. Normal Voices can contain any kind of waveforms, normal Voices can have their Elements assigned to an XA CONTROL option.

There are groups that you can create for Elements so that some can be set to cycle while others do not. Following is a short guide on working with XA CONTROL and its Element Groups.

XA CONTROL is found in a normal VOICE
Press [EDIT]
Press [1] to view Element 1 parameters
Press [F1] OSCILLATOR
Press [SF1] WAVE

ELEMENT GROUP
The "Element Group" works as a parameter in the Xpanded Articulation Control (XA) function.

Element Group
Determines the group of the XA mode so that the Elements of the same group are called up in order or randomly. Assign the same group number to the Elements having the same type of XA mode.

The setting here is not available when the XA mode parameters of all Elements are set to “normal.”
Settings: 1 – 8

Translation: Any Elements that you place in the same ELEMENT GROUP will be treated as a set. For example, let’s say you are using the XA (Xpanded Articulation) called "wave cycle". This particular articulation will play the Elements one after the other: 1-2-3-4-5-6-7-8, 1-2-3-4-5-6-7-8, and so on. If you play a single note and repeat it you will hear the Elements play in order...

If however, you place the first 4 Elements in Group 1 and the second 4 Elements in Group 2, then each cycle will include two Elements simultaneously. 1+5, 2+6, 3+7, 4+8 and then it would repeat. That same single note repeated pattern will cycle but two Elements will trigger for each single note.

If you place the first two Elements in Group 1, the next two in Group 2, and the next two in Group 3, and the next two in Group 4... then each cycle will have 1+3+5+7, 2+4+6+8 and then it would repeat. That same single note repeated pattern will cycle with 4 Elements triggered for each single key press

Or in another situation you may want Elements 1-4 to play a "wave cycle" (one after the other in order) while Elements 5-8 play "wave random" (in random order)... the Element Group function allows this to happen. Simply place Elements 1-4 in Element Group 1, and Elements 5-8 in Element Group 2.