I don't know off hand, but judging by the interfaces for packages like Adobe Audition and Pro Tools, I'm guessing they are using either DirectX or OpenGL.
Here are several screenshots from both Audio Edition and Pro Tools:
The rich colors, sharp details, transparent images, free form layouts, etc., make me think they're using OpenGL or DX! :-)
From: Campbell Barton <email@example.com>
To: Thales <firstname.lastname@example.org>; email@example.com
Sent: Friday, September 27, 2013 1:35 AM
Subject: Re: [Audacity-devel] OpenGL for Rendering Waveforms, etc?
On Fri, Sep 27, 2013 at 3:29 PM, Thales <firstname.lastname@example.org
> Has anyone given thought to using OpenGL for rendering waveforms and the
> like? It would give you full
blown graphical power, which means being able
> to add lots of informative detail. It would also provide lots of
> flexibility for employing things like a volume and pan envelopes, not to
> mention potential for a very eye appealing look (with the help of artists,
> of course.)
> Also, it's compatible across platforms and would give a uniform look.
> I just thought I'd throw the idea out there! :-) I'm curious if it's been
Can you point to any audio applications which use OpenGL for this kind
of display already? (just curious).