Plenty of cities feature live music in their parks during the summer months — indeed it's one of the many joys of the long, warm days of the season. But in a park in Denmark, one can hear music year-round and on-demand. No, not on a stage or in a bandstand, but among the trees.

It's all part of the city of Aalborg's public art project, where trees in the Park of Music host tunes from musicians who have performed at the nearby cultural center. It all started in the 1980s when the city asked visiting musicians to plant a tree as a memorial of their performance.

Since then, over 80 oak and cherry trees have been planted by famous international and less-famous local musicians. In 2012, some of the trees became playable.

How does it work? As Sharon McDonnell writes of her visit to the park, "Simply press the button on the plaque bearing the musician’s name next to the tree, and voila! — you’ll hear a medley of the artist’s hits, like “A Candle in the Wind” from Elton John."

All kinds of music can be heard, from artists like Cliff Richard, Sting, Kenny Rogers, Take That, Rod Stewart, sir Elton John, Vienna Philharmonic Orchestra, Elaine Paige, Victor Borge, Bryan Adams and ZZ Top.

The trees are "played" about 300,000 times a year, proving it to be a popular public art project. It's the only one like it in the world.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.