Nuendo is described as 'Digital Audio Workstation (Daw) specifically designed for film audio post, ADR, re-mixing, surround mixing and mastering. Similar to Audition and Fairlight'. There are eight alternatives to Nuendo for a variety of platforms, including Mac, Windows, Linux, iPhone and BSD. The best alternative is DaVinci Resolve, which is free. Other great apps like Nuendo are Reaper (Paid), Ardour (Freemium, Open Source), Adobe Audition (Paid) and Avid Pro Tools (Freemium).
Ardour is a hard disk recorder and digital audio workstation application. It runs on GNU/Linux, Mac OS X, and Windows. Ardour's intention is to provide digital audio workstation software suitable for professional use.