This was my susbmission for this year's package jam organized by the League of Extraordinary Foundry VTT Developers.
from provided README.md :

Foundry Virtual Tabletop - Track-Tracker module

This module for Foundry Virtual Tabletop adds new functionnalities to the Playlist Sidebar.

It's main purpose is to display a progression tracker for each currently playing track. It also adds some other related features and, as a result, changes the overall layout of the "currently playing" pannel.

Other features include a mark-in / mark-out system (to only play selected parts) available from the context menu. The current time is displayed in a tooltip over the tracker. Also a mute button, because why not.

Basically, goes from this ⇩......................................to this ⇩

⚠ Might be unfriendly to the build-in fade system when trying to use marks AND fade.

⚠ Might be unfriendly to other modules that override the playlist side panel.

⚠ Once a mark-in has been added, clicking the tracker before the mark won't let your hear the beginning of the track and will resume playback from the mark in. Clicking after a mark-out however, should work.

⚠ Still some unwanted behavior/bugs when updating a sound while it's playing.