Summertime — when my brain goes on hiatus — is when I let serendipity become my musical guide. I'm moving a bit slower and taking in the scenery. Instead of seeking out CDs and LPs, they'll find me — and send me orbiting out of my usual classical-music comfort zone.

Hey, anything to escape the routine of an 1812 Overture concert.

I can't recommend this approach highly enough. You'll be out at a flea market on Lombard Street, browsing at a garage sale, or ducking into a secondhand music store on a hot day when you come across something that time, and the music industry at large, has utterly forgotten. The sheer oddness will grab your attention. And for one reason or another — blame the heat — it must be heard.

What could be more fun that listening to a great artist head down a blind alley? During winter months, do you have time to hear jazz pianist Erroll Garner trying his hand at improvising on harpsichord? No, you don't. But in the summer? Yes, I bought that album.

Barbecues are great for LPs like my bargain-bin find Co Star: The Record Acting Game. This one has stars such as Tallulah Bankhead playing scenes from Hedda Gabler that leave gaps in the dialogue for you and your guests to fill in as her leading man.

Failed Broadway musicals somehow make better sense during the summer, with their delirious decisions made on a grand scale — such as the 1971 Prettybelle, with Angela Lansbury as a happy psych-ward inmate writing memoirs titled "Rape and Resurrection" and singing showstoppers like "When I'm Drunk I'm Beautiful." That original-cast CD incongruously turned up on at an odds-and-ends table at the Annenberg Center when I was at a world music concert. What was it doing there?

Marginalia, you say? Never! How can you truly understand the artistic Everests of this world until you've traveled in the foothills — or fallen into the sink holes?

That's exactly where I am when exploring the bargain basements of used-record stores, where it's best to be up to date with your tetanus shots.

No, this isn't a veiled reference to one of Philadelphia's foremost musical basements, Repo Records at 538 South St. Cleaned up in recent years (and temporarily closed at basement level as I write this, but set to reopen this week), it's a cool place to beat the heat, and yields treasures such as a disc in my collection on something called Latimer Records — a live recording of a 4 a.m. 1962 Dean Martin/Frank Sinatra/Sammy Davis Jr. nightclub show in Atlantic City, once a giveaway premium at Philadelphia's Latimer Cafe.

In record-auction circles, this disc is known as one of the most inebriated, semi-functional Rat Pack performances ever recorded. I wouldn't have wanted to be there, if only because of Dean's cigarette smoke. But on my less-spiritual days, when I need some schadenfreude (or, as Susan Cheever calls it, "drunkenfreude"), only this will do.

Car rentals are a great source of happenstance music. Half the time, when you pop in one of your own discs, you find one that somebody else has left behind. My most cherished find, sincerely, is a Chinese punk-rock disc.

The language's innate percussiveness sounds angry even when it's not. You may wonder, in a country that's rolling in so much money, what people have to howl about. But the Mao years must've left scars somewhere, which explains a group titled Brain Failure singing "Anarchy in the PRC." Or a girl group named Queen Sea Big Shark. At least, that's who I think is on the disc — since I don't read Mandarin and had to match what I heard with groups posted on YouTube.

High on my list of specialized music blogs that I hit this time of year is "Big 10-Inch Record" (big10inchrecord.blogspot.com), a 1950s treasure chest of 10-inch records, full of names I haven't heard since childhood (Vic Damone, Gordon MacRae), plus roughly 11 albums by Eugene Ormandy and the Philadelphia Orchestra, all pre-stereo, not likely to be re-issued on CD, and in uncharacteristic repertoire like Haydn and Honegger.

But the big discovery on "Big 10-Inch Record" is the 1954 Johnnie Ray at the London Palladium. This bluesy,  Oregon-born shouter is a summer-sweaty precursor to Elvis Presley, with girls screaming with Beatlemania intensity at the slightest suggestion of anything sexual. Ray faded in the 1960s, died in 1990, and, in the ultimate sign of obscurity, has yet to be anthologized with a box set. True, he was plagued by the IRS, alcohol problems, and homosexuality rumors. But that stuff only solidifies a posthumous reputation. More on him later.

Why do some things survive and others don't? Artistic Darwinism looks different when seen from the bottom up. Some bargain-bin music seems to be an answer to a question, but the world forgot what the question was. Les Paul and Mary Ford go into overdubbing overload with voice and guitar in their early 1950s Bye Bye Blues album, but now it seems chillier than a Texas air conditioner.

Technology can be the problem. Digital remastering bleaches out Doris Day's voice into something like an overexposed photograph. I never would've known that had I not stumbled upon a street vendor who appears in the warm-weather months around 15th and Spruce Streets, and whose Doris LPs reveal vocal details and shading that put her miles above many pretty-voiced singers of the 1950s.

Often, careers end on the wrong foot. Peggy Lee (1920-2002) whispered through her final years. Only when another street vendor last month sold me her 1956 Black Coffee album did I understand her understated genius.

Jo Stafford (1917-2008) is so reassuring, her records could cure PTSD. But Stafford ended her career with a self-created alternate persona named Darlene Edwards, the most intentionally (and hilariously) horrible lounge singer ever imagined. What else could possibly follow Bankhead's Hedda Gabler at the barbecue? Alas, for Stafford, Darlene was a bad move in the long run.

Mabel Mercer (1900-1984) is one of the most idolized cabaret singers of our time. But her most-circulated recordings show a disassembled combination of a worn voice, Shakespearean enunciation, and contrived soulfulness. Not until you stumble across the older recordings do these elements emerge as all of a piece.

Durability, however, also depends on how many ways the artist has seeped into the culture. The following analogy may seem like a massive digression, but stick with me: One friend of mine makes a full-time living by impersonating the Statue of Liberty at street fairs. Besides the gown, crown, and green makeup, the key to impersonating the statue lies in the face: She needs to resemble Elvis Presley circa 1958.

Unlike Elvis himself, Lady Liberty needs no depth or dimension to secure a place in our culture. She has one pose, one meaning, and one location as she symbolizes the freedom we all want.

The Elvis Presley impersonators, in contrast, come in endless varieties. Some are female, some African American. And yet the Elvis brand, far from being diluted, is hotter now than at his 1977 death. That's because Elvis is such a multidimensional figure: Whether we connect with his artistry, sex appeal, or attitude, he continues liberating parts of ourselves. He's embedded in our consciousness like a tree with countless roots.

Why, then, did that proto-Elvis, Johnnie Ray, fade so completely? I tried binge-listening. Even with all the summer leisure time in the world, you can't do it. Five songs, and you've had enough, because as time went on, he did the same kind of shouting with every song. In contrast, Elvis could do everything but sing opera. So history has turned the page on Johnnie Ray. At least for now.

The past may, indeed, be a foreign country, but it's never over, at least when the music survives on some medium that can be rediscovered.

Consider the Shaggs, the teenage all-female New Hampshire rock trio who made their 1968 album, Philosophy of the World, at a point where they barely knew how to play their instruments. Yet that once-hapless album, only 100 copies of which were circulated, serendipitously fell into the right hands — like those of powerful DJs, not to mention Frank Zappa. Now, nearly 50 years later, the Shaggs are a paragon of guileless, unfiltered outsider music. They were even dramatized in an off-Broadway bio-musical titled The Shaggs: Philosophy of the World.

The other day, I saw their album in the window of Academy Records in New York City, selling for $60. And it all starts in the garage sales, basements, rental cars — all ad-hoc museums of orphaned culture.