Join WCRB at the Hatch Shell on the Esplanade this summer for free concerts with the Boston Landmarks Orchestra.

Also in this link roundup: a lioness gets a serenade, a textbook math question has a Beethoven problem, and the Philadelphia Orchestra gets sorted. Onward!

Plus, we'll complicate "Happy Birthday," hear a viral opera-singing Uber driver, and find out how to hear the symphony for free, all in this link roundup! 

Long summer days mean more hours you could be spending outside, and every outing needs a good playlist, don't you think?  Here's what we've been listening to lately -- cool music for hot summer days. 

Augustin Hadelich's latest album of violin concertos offers two unlikely bedfellows. The tuneful, romantic classic by Johannes Brahms bumps up against the modernist mayhem of György Ligeti. The album, titled simply Brahms, Ligeti: Violin Concertos, also proves to be a compelling introduction to one of today's best, but still undervalued, violinists.

This month in Tulsa, Okla., opera singer Lucia Lucas made her U.S. debut. She also made history.

At the Tulsa Opera, Lucas sang the title role in Mozart's Don Giovanni. Mozart's character is a ruthless, macho womanizer. Lucas is a transgender woman with a rich baritone voice and is the first known trans woman to sing a principal role on an American opera stage. In a conversation with NPR's Ari Shapiro, Lucas said she doesn't want her performances to be entirely defined by this historical marker.

Olivier Latry, one of the chief organists at Notre Dame Cathedral, was the last artist to record on the famous instrument before the catastrophic fire on April 15 that damaged the church and caused its spire to collapse. This pipe organ is the largest in France and dates back centuries. Though it was spared from the flames, it will still require extensive renovation.

Baroque violinist Thibault Noally has played with many of the most brilliant artists in the early music world, and the wisdom he has absorbed now serves as a guiding light for his own three-year-old ensemble Les Accents on WCRB's CD of the Week.