Wow in depth, with enough info to base an entire campaign around. It's nice to see an unusual enemy that has a fresh approach to achieving their goals, and really make players struggle to get a grasp on their capability and motivations.
A couple quick ideas to improve the appearance/presentation:
Putting the headers such as appearance, confrontation etc.. in bold would help a bit to highlight the different sections of the article and make it easier to find a particular area when skimming during a game session.
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Also, putting a line break in between each plot hook and bolding their titles would make the last text area a bit easier to read/navigate. (as it is it's a bit of a wall of text towards the end)
A unique take on a gnomish subclass, and can make for a refreshing change in the usual wilderness encounter.
Perhaps giving them some type of musical related magic would help fill in the missing gap? Perhaps they have found a way to combine bardic magic with that of regular mages?
A song of burning passion may possibly set a target on fire, or one of a raging river make those enemies in ear shot feel as if they are drowning?
Giving them a little bit of offensive power (which they learned so they don't suffer the same fate as their ancestors) could make the odd group who looks at them as little push overs rethink their assumptions rather quickly. (Having a group of singing gnomes come to the rescue from a bandit ambush would also make for a fun encounter.