Thanks for the plug, Vic.

ABC2NWC is available here http://www.abacusmusic.co.uk/. Unfortunately, it is a bit out of date and will only deal with the old Noteworthy version 1.75 format not the new version 2. It can still generate Noteworthy files that the new version can read but cannot generate ABC from the new Noteworthy files. I'm working on it.

As a stopgap, I have written a User Tool for use with Noteworthy 2 which is available free from The Noteworthy Composer Scriptorium. This is a bit fiddly to install; get in touch with me if you need help.

There is also a simple ABC editor player and printer called ABACUS available from my website which displays notation as you type in the abc.

Neither ABC2NWC or ABACUS can handle nested tuplets. Sorry about that.