@Iggy
I'm not familar with Octamed, but I have seen Audio Evolution (another Amiga music program). Currently, AE is available on AOS, MOS, AROS, Windows and OSX and the non-Amiga versions are more advanced and continue to be developed.
You're talking chalk and cheese I'm afraid. AE is very good, but it's a multitrack recording system with MIDI support. OMSS, on the other hand, is a multichannel tracker with MIDI support. The former is primarily for production, the latter is primarily for composition. OMSS may be years old and look "primitive" to people that have never used it, but trust me, a person couldn't be more wrong for thinking it. It's one of the finest pieces of software ever written for quickly getting your ideas down.
You can't just magically go from OMSS to AE, they work in completely different ways and are built for totally different purposes. If you use OMSS to compose, the chances are you would also use AE for post-production work / live instrument / vocal mixdown.
Like Tension, I also use OMSS and don't have any serious time for an Amiga compatible OS that doesn't run it. An OS is there to support your applications as much as it is to support your hardware.