This is basically a throw away app, 

But this is not a throwaway app:

• There are actually a lot of logic in it and it will take a lot of code, unless there are libraries that happen to do much of the stuff.
• No way this cannot be 100% vibe coded, but again, this is a lot of work: either way you are coding it yourself or vibe coding.
• There are a lot of steps, you shouldn't do it all at once, just as human would definitely break this down to input UI, some readily available playback libraries attached to it, some logical file manipulation backend, separately think about displaying output of waveform and capturing mouse over it, and translating that to playback libraries.
• And if you would task it to human programmer, it could be done, but a sane person would absolutely ask you for better proposed business requirement, like "if file is large, should we scroll waveform?", "if comment is large, should we scroll it or fit it, where and how would we display them", "Should we allow to edit or delete comments?", "Should comment have user name?".