GEOFF BENNETT: Traditional piano recitals can sometimes be intimidating for performers and audiences alike.

Two California pianists have made it their mission to use outdoor spaces to make them less formal and more accessible.

Special correspondent Mike Cerre reports from San Francisco on the crescendo of support for this approach, part of our arts and culture series, Canvas.

MIKE CERRE: If you dare to place 12 concert grand pianos in different botanical garden settings and invite people to come play and hear whatever piano music inspires them, they will come.

(APPLAUSE) MIKE CERRE: Hundreds of pianists from all music genres and thousands of piano music devotees have been descending on San Francisco's Botanical Garden for 10 days each September for these freeform, all-day piano recitals called Flower Piano.

DEAN MERMELL, Co-Founder, Sunset Piano: So that whole kind of recital vibe is kind of subverted with what we are doing.

ANGIE WONG, Audience Member: I had fun.

TRENT HU, Audience Member: It's just a mature, comfortable environment to share with friends.

MIKE CERRE: Dean Mermell and Mauro Ffortissimo share a common love of the piano and a healthy disdain for indoor piano recitals confined to overly controlled environments.

MAURO FFORTISSIMO, Co-Founder, Sunset Piano: Things in a concert hall, people are kind of quiet and don't move and they're kind of stiff.

I think it's a bit liberating to play outdoors.

MIKE CERRE: Mauro Ffortissimo is a transplanted Argentinean pianist, sculptor and performance artist.

He started this outdoor piano movement by clandestinely putting a piano on a bluff along the Northern California coast near his studio, so he and others could play in nature.

MAURO FFORTISSIMO: And to hear the waves crashing, the tide coming and going, and you play and you breathe along with that, it's quite an experience.

MIKE CERRE: For an encore, he and Dean Mermell put 12 pianos out above the coastline the following year, this time with official permits.

And even more pianists and spectators came.

MAURO FFORTISSIMO: Newspapers, TVs, radios, they all came, and it became a big thing.

And it gave me my 15 minutes of fame.

MIKE CERRE: It also caught the attention of San Francisco city officials and art patrons looking to celebrate its Botanical Garden's 75th anniversary with something special and participatory.

MAURO FFORTISSIMO: The idea is just to invite anybody to play.

So this is also a difference with a concert hall.

This is audience participation, in the sense that they come from 9:00 to 5:00.

Anybody could sit on the piano and play.

MIKE CERRE: From 12:00 to 3:00 during the daylong sessions, several of the pianos are reserved for professionals, like Hunter Noack.

He has been doing piano recitals in unique open spaces around the country.

Most of the performances are more spontaneous.

Joseph Torres took advantage of the setting and the moment to play before a public audience for the first time.

JOSEPH TORRES, Amateur Pianist: I was being pushed by my friends here, who were telling me to play.

That's the most difficult thing for me is getting over the nerves to play in front of other people.

DEAN MERMELL: A lot of children and a lot of adults have never played in front of people before.

The only place they have ever played is with their music teacher or in front of their girlfriend and their - - or in my case in front of my cat.

MIKE CERRE: Pianist and composer Kennedy Verrett incorporated the Botanical Garden's elements in his original composition celebrating the role nature can play in music.

KENNEDY VERRETT, Composer: So our purpose here is to highlight that and to also be in concert with not just ourselves, but with the birds, the sword ferns, and with these ancient relics.

MIKE CERRE: So I know I'm in New Zealand, but I have got to get to Africa.

I hear some boogie-woogie and some classical music.

STEPHANIE LINDER, CEO, Gardens of Golden Gate Park: Everyone gets lost trying to find the piano.

MIKE CERRE: Stephanie Linder heads the Gardens of Golden Gate Park, where Flower Piano has become its largest annual event.

STEPHANIE LINDER: We have 55 acres and 12 pianos, and they're tucked in all different nooks and crannies.

But they find their way.

And the music sort of guides them.

MIKE CERRE: This combination of the environment and the performing arts, how important is it for the people to come here?

STEPHANIE LINDER: Well, it's really important.

I mean, we see public gardens as a public health strategy, and we know that being in places like this lowers your blood pressure, lowers your cortisol, stress hormones, activates your brain in ways that it normally doesn't work.

And so music does the same thing.

And you combine those things, it's pretty spectacular.

MIKE CERRE: Take this improvisation by Harry White, a lifelong pianist and retired city gardener, who stopped playing at home because of his progressing Alzheimer's.

Along with his wife and caregiver, he was able to find and play all 12 pianos during this year's Flower Piano.

DEAN MERMELL: I have come across children so young here that they had to sit on a stack of their music books just to play, and they couldn't reach the pedals, of course.

It's pretty mind-blowing to see that connection of music starting to happen at such a young age.

MAURO FFORTISSIMO: You know, as a kid, I went to conservatory for five years, and we couldn't -- we didn't have a piano at home.

And, eventually, my parents bought a piano.

And I remember seeing them coming down the street, pushing a piano with a few friends, full -- all bright.

And I was so happy.

And, yes, I kind of knew then that, yes, I could get along with the pianos the rest of my life.

MIKE CERRE: Mauro's lifelong love affair with the piano includes salvaging discarded pianos he collects and restores for these outdoor events otherwise destined for the dump and landfill.

DEAN MERMELL: I like to think the composers would like it, because it lets people experience it in a new way, in a way that they can approach it with a sense of wonder, because what's that piano doing under this tree?

You know, it's not -- it's the kind of thing where it kind of short-circuits your brain for a second and lets something else come in.

MIKE CERRE: By taking a piano out of its comfort zone, these Flower Piano events are connecting piano music to more people each year in their comfort zone.

For the "PBS News Hour," I'm Mike Cerre in San Francisco's Golden Gate Park.