17 (Penetration) (a.k.a. Penetration) is an unreleased instrumental track recorded on 5 December 1988 at Paisley Park Studios in Chanhassen, Minnesota (during the same session as 18 (R U Legal Yet?), three days before 19 (Jailbait)), during sessions for Madhouse's third album 24. The track was included as the opening track on the album 24 (the number in the track title sequentially follows Sixteen, the final track on Madhouse's second album 16), before the album was abandoned.
On 21 January 1991, Prince submitted the track (now re-titled Penetration) to Miles Davis, along with Jailbait and A Girl And Her Puppy, for his consideration. Prince wanted Davis to record additional trumpet parts before sending them back. Davis instead taught the three tracks to his band, and they recorded new versions of the tracks on 27 March 1991 in a German studio. The band also played them regularly on Davis' 1991 tour. After Davis died in 1991, Warner Bros. asked Prince to add some post-production to this track (as well as Can I Play With U?, Jailbait and A Girl And Her Puppy) to include on his first posthumous album, Doo-Bop, but Prince was not interested in contributing to tracks that he felt didn't show Davis at his best.
A live version of the track, recorded on 10 July 1991 at La Grande Halle de la Villette in Paris, France, was planned for release as the 71st track on a 2001 box-set of Miles Davis' Warner Bros. work, entitled The Last Word, but the track was not included on the eventual 2-disc 2010 release, titled Perfect Way. As the original Madhouse version remains unreleased, the Miles Davis versions are included here instead of being considered straight cover versions.