Well, after five years I'm finally making good.
"Splash" was recorded on November 12 1968 in Columbia's Studio B, with Miles's then-touring band: Wayne Shorter, Dave Holland, Chick Corea, and Tony Williams; Herbie Hancock was added to the session as a second pianist.
An edited version of "Splash" was included on Circle in the Round, a compilation of various materials that was released during Davis' hiatus in the late 1970's. (Water Babies and Directions are similar collections.) But the full take was unreleased until 2002's Complete In A Silent Way Sessions.
It's something of a myth among jazz musicians that Miles Davis didn't actually write any music, that all of the tunes attributed to him were actually written by other people. But this is to take a few cases (Solar, Four, perhaps Blue in Green) and draw a false conclusion (some, therefore all). Miles was an accomplished and thoughtful writer, evidenced even in the late 40's with "Donna Lee". His work in the late 60's is groundbreaking in the way it embeds open modal improvisation within a larger composed scheme. Other tunes that do this: Frelon Brun, Shh/Peaceful, and the Ghetto Walk, all from 1968.
Paul Tingen describes "Splash" as "almost a cross between 'Two Faced' and 'Dual Mr. Anthony Tillmon Williams Process,' [both recorded the previous day - ME] employing both the stop-start device of the former and echoes of the twist rhythm in the latter." (2001, p. 53)
Download Splash (Concert pitch).