Taskmaster's powers are generally described as photographic reflexes in every comic with him that I've read. This generally means that he can mimic any action he sees, as soon as he sees it. It does not allow him to perform actions that he is not physically capable of performing.
For sound, wikipedia has an un-cited example of him being able to mimic voices, so it may be possible. Given the stated way that his powers work, he would likely need to see a human(oid) with a similar vocal tract making a sound to be able to mimic it.
Watching an accountant would probably given him the enter numbers in spreadsheets like a pro, but not necessarily know what numbers he should enter (he does generally get some ability to predict the next moves of his opponents by copying them, but I think it would be a stretch to apply that here).
As with any comic book power, the exact nature of it is guaranteed to change a bit between writers and over time.