The flip flop provides a DC pulse which finds itself momentarily trapped in an inductive- capacitive contraption, where it expires slowly. Playing around with various values can yield some interesting results. The output isn’t very high, so the volume needs to be increased significantly. Be aware that some circuit adjustments while the chime delay is running may introduce temporary but loud crackles while the system adjusts. Just remember to pull back on the volume prior to Deleting or inserting new or different components. The diode was inserted to ground out an annoying DC click just as the chime sound faded. Enjoy!