Yes, exactly! So I understand they were removed on purpose? I really miss the jingles, they gave a real vibe and experience of achieving something. (for example: https://runescape.wiki/w/File:Wilderness_task_hard.ogg or https://runescape.wiki/w/File:Varrock_tasks_all.ogg)
We could theoretically reinstate those by triggering them from the area task code that flags the area task variable and achievement popup. Actually quite surprised they didn't continue to occur. (Presumably these special jingles were more deeply embedded in the old task system and didn't survive when we created a new achievement system.)
For clarity's sake, did these jingles happen when you completed the last achievement in a difficulty set, or when you claimed the reward from the task giver for that set?