A small introduction:
This could have been a "What is a ??? Word™" question, but I decided to give it a little twist. The first part is simply about finding out what makes the short words Tonal (although I decided later that "Notable" might be an even better description, so wherever you read "Tonal" you may also read "Notable"). The poem will help you as you go along.
Complete all tonal words below,
List their options in a row.
Numbers for letters is what you need,
They indicate what you should read.
Just take these, strike out the rest,
Now you have fulfilled your quest.
N.B.: All tonal words can be found in this English dictionary.
P.S.: Here is a text version of the picture above:
TONAL -> LUNATIC LEACH -> SARCASM HEAP -> SASHIMI ROLL -> PLATEAU VERY -> COMPLEX RISKY -> COMPLEX HOST -> THOUGHT READ -> ATTEMPT MEND -> REVISIT ARROW -> FORTIFY LIGHT -> WONDERS GO -> DYNASTY LOVE -> OUTDRAW RACE -> PONTIFF OLD -> COUTURE OWN -> ANALYZE LONG -> VOUCHER ROOM -> ENCRYPT STRAY -> HUNDRED LASH -> SPECIES RANK -> SANDBOX ROUND -> NOTABLE
Finding out what makes the shorter words tonal/notable is key.
The tonal/notable property is related to the fact that these words are incomplete.