-istically

Alternately -istical (“adjective suffix”) + -ly (“adverb suffix”) or -istic (“adjective suffix”) + -ally (“adverb suffix”). In either case, ultimately -ist + -ic + -al + -ly.

-istically

1. Used to form adverbs describing action in the manner of the root adjective; use is identical irrespective of whether the root adjective ends with -istic or -istical.
   • 2003, Don Michael Randel, The Harvard Dictionary of Music, page 598:

     Horns, trumpets, and trombones, both soloistically and sectionally, became central to the orchestral concept... His highly subtle orchestration elevates woodwinds, more often scored soloistically than sectionally.