TSE3 stands for the Trax Sequencer Engine version 3.00.
The library provides facilities to record, edit and playback MIDI musical data. It contains powerful facilities to manipulate the MIDI data in real time. It provides an advanced and acclaimed object-oriented structure. It provides support for such facilities as on screen keyboards, on screen VU bars, a 'mixing desk' and so on.
TSE3 can be used to create a full sequencer application, or a simple music file playback utility.
The main TSE3 API can be found in the TSE3 namespace. This namespace contains a number of sub-namespaces, TSE3::App, TSE3::Cmd, TSE3::Ins, TSE3::Plt and TSE3::Util, which provide extra services over the basic TSE3 API. (There is also an internal implementation namespace TSE3::Impl which you can safely ignore).