it's one of those objects that is in Pd but could be easily dealt with in Pd without the external (...) but it's basically a line~ with an offset, and a fixed rate

looks like~ cyclone's count~ but much simpler

it just generates a signal ramp with the right characteristics to patch it into tabread4~ and playback samples at their original pitch.

or using it with tabread~ then instead pf tabread4~

looks again like count~ as one of its applications is in conjunction with index~ (basically tabread~).

There are quite a lot of externals like this (and some from me) where people coded something in C for convenience, but can be easily done in Pd without externals.

I know... Pd Extended is filled with things like that, and to make it more of a deal, documentation is sometimes bad, when simply non existing.

I'm willing to help this in the forth coming Purr Data, by reorganising it and making it better documented

cheers