Personally, I prefer the current round buttons to your rounded squares. However, I think the graphics which you propose give us a chance for improving the current GUI.

- buttons.png (60.11 KiB) Viewed 10430 times
On the top left is the current design. Below that I pasted your original as copied from this thread and overwrote it with the default depressed Play button and then alternate darker-grayed green fill. On the top right are your buttons shrunk down (maybe a bit too much) to fit the current sizing. At the bottom right are my tentative thoughts about visually presenting the Skip To buttons such that it is visually obvious when the cursor is at one end or the other of the track – the darker purple is "able to be pushed" the light gray–purple is "disabled".
Note that you did not present depressed versions of your icons. Note also that some of the icons are "momentary" and do not stay depressed and thus do not need depressed versions.