Ritchie Blackmore tribute
The song's name is Son of Alerik and it cannot be found on any Deep Purple album except the remastered version of 1984 album Perfect Strangers, released in 1999.
I remember reading somewhere that this song was also the B side of a limited edition of the Knocking at Your Back Door single in the 80's - don't think that this is still available though.
Also, there is, to my knowledge, no live footage of this song as it was never played live and was probably only played once in the band's entire history. The video just mixes some some parts of the 1986/87 perfect strangers tour with snippets of Rainbow gigs publicly available on YouTube.
The origins of the song are unknown but it is said that it's the result of a Jam session they did while they were bored in the studio, so this isn't a song that was written, just improvised. These guys were true musicians and artists and the music speaks for itself