FZ album(s) in which song has appeared:

• Philly '76 (2009) as The Purple Lagoon, also heard at the end of Dinah-Moe Humm and Muffin Man, performed in Philadelphia, October 29, 1976
• Zappa In New York (1978) as The Purple Lagoon/Approximate, performed in NYC, December 28 and 29, 1976
  • same version on Läther (1996) as The Purple Lagoon
• BTB I: Saarbrücken 1978 (1991) heard at the beginning of Dancin' Fool, performed in Saarbrücken, September 3, 1978

Tour(s) in which song is known to have been performed (main source: FZShows, v. 7.1):

• October-November, 1976 (North America)
• December, 1976 (New York)
• January-February, 1977 (Europe)
• January-February, 1978 (Europe)
• August-October, 1978 (Europe & North America)

Comments:

Touring versions from Foggy G's We're Only In It For The Touring:

1976 Oct-Nov
This song is used as the opening number of each show, which Frank would use as the background music to the band introductions. It also frequently found itself as the closing tune of each set, and as the closing tune of the encores. Obviously, this is not the full-blown extravaganza that we have on ZINY, but just a short run-through of the main theme.

1977 Jan-Feb
This tune is used as an opening and closing number only, i.e. the full-blown extravaganza found on ZINY is not what we get here. Instead, we get the main theme performed by the band, with Frank doing the band introductions, and an occasional short guitar solo, over the music. The tune varies in length according to the length of Frank's solo and/or introductions.

1978 Jan-Feb
This is just the main theme, as played on ZINY. This was played as the opening tune of every show, which Frank used as the background music for the band introductions.

1978 Aug-Oct
In the early shows of the tour, this was used as the opening vamp for the band introductions, similar to the way it was used on the previous tour. Occasionally, prior to the actual introductions, Frank would rip off a short and rather pointless solo. About two weeks into the tour, however, Frank substituted this tune with an actual guitar solo spot, either composed on the spot or contained within a song that was essentially a vehicle for a guitar solo (i.e. "The Deathless Horsie").

Structure (ZINY version) by Jon Naurin:

Purple Lagoon is one of the two themes that's played against each other in the head of the song. It was the "tour theme" for the fall '76, spring '77 and spring '78 tours, but the special medley arrangement with Approximate was only played at SNL and the Christmas shows at the Palladium in Dec 1976.

Here's a dissection of the ZINY version:

0:17 - 0:36	The Purple Lagoon
0:37 - 1:16	Approximate (O'Hearn keeps playing PL until 0:46)
1:17 - 15:23	Solos, over the Pound For A Brown vamp
15:23 - end	Purple Lagoon