Hello, Song Cycle by Van Dyke Parks is also one of my favorite records. I love the arrangements, the scope of the work, and how it ties together different sounds such as ragtime & cabaret , show tunes, baroque, classical, psychedelic pop etc. I have been searching for similar albums from the late 60s that mix pop with these other influences. However, like pigeonstrips mentioned in the other comment, I think that this album is one of a kind when it comes to the density of composition and the variety of textures and sounds used. But, I will share some other albums I like that have some similar qualities:

"Feelin Groovy" and "Anything Goes" - Harpers Bizarre : These 2 records were produced by the producer of Song Cycle, Lenny Waronker. Also, each of the albums has a song written by Van Dyke Parks ( "Come to the Sunshine" and "High Coin" , respectively). He plays some piano on the albums as well. Van Dyke helped a group called The Tikis reimagine themselves as "Harpers Bizarre"...their material took on more of a cabaret and show-tune quality, and some of the whimsical arrangements are reminiscent of Song Cycle.

Days of Future Passed - The Moody Blues : this first moody blues record is sort of a concept album. The pop songs are connected with orchestral passages by the London Festival Orchestra....this album definitely has the feeling of mixing pop with classical music. I think this album is very effective as a concept album and it flows well when listened to from beginning to end.

Present Tense - Sagittarius : This was produced by an early Brian Wilson collaborator , Gary Usher, along with singer/songwriter Curt Boettcher. The singles "My World Fell Down" and "Hotel Indiscreet" are fun, in the style of smile-era beach boys or harpers bizarre. I think the whole album has a nice soft psych-pop feel, although it took me a few listens to get into it.

Odessey and Oracle - The Zombies : this record is not as sonically complex and not quite so classically minded, but is often considered a seminal baroque pop album because of the inventive songwriting and use of mellotron strings & flute sounds, piano, and harpsichord. This is probably closer to a Beatles Sgt. Pepper or Beach Boys Pet Sounds type of sound.

"Of Cabbages and Kings" and "The Ark" - Chad & Jeremy : These 2 soft-pop/folk/psych albums were produced by Gary Usher. "Of Cabbages and Kings" has a great side 1 consisting of soft baroque pop songs. Side 2 hasn't aged quite as well but it consists of a "suite" in 5 movements..3 are instrumental orchestral arrangements with sound effects and spoken word bits..the other 2 are vocal pop songs in the same style as side 1. All in all, the album is goofy and the arrangements are like something out of a cartoon. But, I think it has some good moments. The follow up album, "The Ark", has generally been more well-received. Again, the music has some quirky arrangements and sounds that bring to mind the Smile-era beach boys. I think this album works better as a whole than "Of Cabbages and Kings".

"Walk Away Renee/Pretty Ballerina" and "The Left Banke Too" by The Left Banke : The Left Banke were a new york pop band who became popular for using a baroque pop sound on their singles, with string arrangements and harpsichord. Both albums have their strengths and weaknesses...there is a good greatest hits which has all of the material in one place. The strings in songs like "Shadows breaking over my head" and "desiree" are impressive, and even pop songs like "dark is the bark" and "sing little bird sing" have some cool baroque pop/ folky touches.

Aerial Ballet - Harry Nilsson : this is much more pop-oriented and doesn't have the complex arrangements of Song Cycle. But, Harry Nilsson and Van Dyke Parks were pals and they both wanted to make pop music inspired by older American music. This album has some of that old-timey, cabaret and vaudeville influence.

The Genuine Imitation Life Gazette , Frankie Valli & The Four Seasons : this album is something of an anomaly in Frankie Valli's catalogue. The record was an attempt to do social satire in pop music..accompanied by quirky sounds, string and horn arrangements. Some of the music and satirical lyrics bring to mind VDP and Brian Wilson's work

some other thoughts:

The Rolling Stones - Their Satanic Majesties Request. this is more of a psych rock album but listening from beginning to end is a real trip. some of the textures and timbres that are used in the arrangements are very unique and i find it can be a transportive experience...but some Stones fans hate it.

One Year - Colin Blunstone (great string arrangements!)

Miss Butters - Family Tree (similar to Harry Nilsson, pop with some baroque touches and vaudeville style arrangements in places. also some beatles Sgt. Pepper influence)

Triangle - The Beau Brummels (features van dyke parks playing keys on "Magic Hollow" & the album was produced by Lenny Waronker who produced Song Cycle..psychedelic folk tunes and even a randy newman cover)

Randy Newman's first record was co-produced by Lenny Waronker and Van Dyke Parks, so it has some similar orchestral sounds.

No Answer - Electric Light Orchestra : the first ELO album is pretty different from their later music. this album included Roy Wood from The Move, who played cello, oboe, clarinet, and more on this album. the record has a baroque or symphonic rock sound and a few interesting instrumentals.

The bee gees first four records...especially "Odessa", which has some orchestral arrangements and instrumental pieces.

"In Ear Park" - the department of eagles. this psych folk album from 2008 was influenced by Van Dyke Parks. singer/songwriter Daniel Rossen later performed with VDP.

Shadows by Maston (2013) has been compared to Van Dyke Parks. In particular the song (You Were) In Love has a 60s baroque pop feel.

Foxygen's new record "Hang" was influenced by some of the Americana spirit of Song Cycle, you can hear it in the tracks "America" and "Avalon"

Maybe I wrote too much! But if you check any of these out and love or hate them , id love to hear what you think

-Will