YOU CAN HEAR AS MUCH in Elton John's music from the small, overamplified speakers of the radio in a rusted-out '69 Dodge as you can from an expensive living-room stereo. That is a major source of his success and his importance. His songs made it big from the dashboards of beat-up, second-hand cars, old bomds parents let their kids take out on Saturday nights, souped-up monsters that squealed out of high school parking lots, cars with steamed-up windows parked in dark woods outside town.

Elton John always had a song on the radio in the first half of this decade. He reached adolescents sitting at home with transistor radios and he reached their older siblings on wheels. Although it is fashionable now to sneer at the musician-turned-glitter star, his influence on popular music was once very real. His popularity did not arise in the beginning out of pure hype. Simple songs of affection like "Your Song" and "Daniel" can still move those who are disposed to be moved. If less memorable, cheerful piano boogie numbers like "Honky Cat" and "Crocodile Rock"set many feet tapping when the American Top 40 smiled on them four or five years ago.

The memory of Elton's power to evoke a mellowness or an up-beat rowdiness, his power to make people buy his records and keep them on the radio, makes Elton John's Greatest Hits Volume II a sad record. It contains little of the spark to be found in his first collection of hits. If Elton's music changed in the first half of this decade from quiet piano-and-voice cuts to glitter-and-guitar tunes, it still had an original fire in it that shows in his first collection, released in 1974. The collection traced Elton's history on the Top 40 from the beautiful "Your Song" through his rise to superstardom and his music's shift toward the loud and outrageous in driving, mindless songs like "Bennie and the Jets" or "Saturday Night's Alright for Fighting."

Sometime after the first collection came out Elton's music lost much of its power, and was left with only the loudness and outrageousness, and his name. He had pumped out too many records too fast. There is a limit to how much original music one man can produce; after a while he starts covering the same ground over and over. He has nothing more to say. Elton's songs started sounding tired. They stayed on top of the charts only because they came from Elton John.

The slide did not begin until around the time "The Bitch is Back" rode up the charts in 1974. The bitch was back, alright, but the bitching sounded a bit contrived. Significantly, "The Bitch is Back" is the first cut on Elton's latest set of "greatest hits," and the song is one of the better cuts on the album. Of the ten songs included, two have something to say, two are fun in a simple, unelaborate way, one is drawn from the early part of Elton's career, and the other five are plainly boring.

The album includes two trashy re-makes of '60s pop songs, "Lucy in the Sky With Diamonds" and "Pinball Wizard," the latter made for the still trashier film Tommy, itself a pathetic re-working of The Who's rock opera. Elton John's name did nothing for these ghosts from the past except make them sell. The originals were much better. Elton's willingness to perform them only showed that his fire was burning out. "Island Girl," an original, was among the most annoying of AM radio's most played tunes. "Don't Go Breaking My Heart," a vapid, iivv number Elton recorded with Kiki Dee, starts nowhere and goes nowhere but takes up four minutes and 23 seconds of air time. In "Don't Go Breaking My Heart" Elton tries to divert the audience's attention from the song's aimlessness by pouring on strings and driving the tune along with relentless loud percussion--the same formula that works for hard-core disco. But Elton John is not a disco king.

The two songs that stand out on his latest set of "greatest hits" are reminiscent of an earlier Elton. They are songs on which he restrains himself from over-orchestrating, holding back the strings, the drums, the guitars and the synthesizers to let his piano and his voice come through. As Elton drove himself to keep putting on a show, he often seemed to forget that he could produce his best music alone. "Sorry Seems' to be the Hardest Word" and "Someone Saved My Life Tonight" recall some of Elton's old power to mellow his audience with simple music, but even on these two songs the studio orchestra ladles on the strings too heavily. The emotional flavor Elton tries to provide though the orchestra is simply cloying.

Beneath the feathered hats and the enormous glasses Elton is known for, apart from the foot-high platform shoes and the carpeted pianos, there has always lurked a moody, but very good singer, songwriter and piano player. Success spoiled him. Somehow the piano player got lost among the glamorous and empty accoutrements of international success.

BUT THE PIANO player knows that. He has always maintained that his best songs were "Daniel" and "Your Song." And now he is returning those roots. He no longer has any songs on the charts, and word is that he now plays simple music in clubs, scorning the charade of strutting for a mass audience. In fact, Elton the piano player wrote a sort of obituary for Elton the glitter king in "Someone's Final Song," on his last regular album,

Blue Moves:

He died when the house was empty,

When the maid had gone.

He put a pen to paper for one final song.

He wrote--

"Oh babe, it's the only way.

I know it's wrong but I can't stand

To go on living life this way."

The king of the outrageous has his farewell on the album. The last song, "Bite Your Lip (Get Up and Dance)" is an all-out exhortation to "move that muscle and shake that fat," and it works. Elton brings in piano, bass, drums, slide guitar, electric guitar, synthesizers, congas, strings, and the Cornerstone Institutional Baptist and Southern Californian Community Choir, to join him in an assault on absolute boogie. The music doesn't really go anywhere, but it's fun while it lasts.