Duration-based task tracking app that emits sound and starts automatically the next task

Question

I don't care if it is strictly web or mobile or both. The functionality is the most important.

I practice guitar and I want to be able to breakdown my practice into smaller bits.

The best way to explain it is; like a workout app in which you have a set of exercises, to dos, that the app will run through in order until completed.

I am looking for a task manager that:

1. each event needs to have its own countdown timer.
2. must have grouping function for tasks. folders, etc.
3. must have the ability to combine multiple groupings into one big active list rundown.
4. MOST IMPORTANT- I need the app to alert me that the individual task is done with some audible sound, but then automatically move on to the next task. I don't want to have to keep pressing next on it, as I plan on having upwards of 50 smaller to dos within a folder.

I have found an app called donow, but it is not very well coded. It supposedly has all the functionality I am looking for but most functions aren't working for me.