Increasingly, there are quite good cross-platform C libraries that abstract system functionality, including:

• fluidsynth (soundFont based sound synthesizer)
• portaudio (audio recording and playback)
• SDL (Simple DirectMedia Layer - a cross-platform multimedia library)
• others ?

In addition, common Operating System platforms such as MacOS X and Windows provide compatible system functionality (e.g. audio, video, networking).

One of the real strengths of Tcl has been as an integration language. The reality today is that is still true if the technology you're trying to integrate with was built in 1995 or earlier. In some respects, Tcl has gone from a "glue" language to a "dried-up glue" language.

But this is changing - Critcl has been used to wrap this functionality behind a higher-level cross-platform API and make it available as a Tcl package. For example, the muzic package wraps fluidsynth, CoreAudio and QuickTime on OSX, and winmm/dsound on Windows.

As part of this exercise in making Tcl more relevant would include a team that extend Critcl’s wrapping abilities (at least, by allowing structs to be returned as dicts and vice versa) and look for opportunities to wrap such cross-platform libraries and system functionality. This would, for example, facilitate the production of a system module.

This might also include a small C compiler such as tcc (reference Mark Janssen’s recent work) - to act as a fallback if there wasn’t a toolchain installed on the current machine, and also to facilitate cross-compiling to Windows on *nix platforms.