Stephen Sondheim, one of the greatest lyricists and songwriters in American musical theater, turned 88 today. In honor of this national holiday, I’d like to draw your attention to one of the best YouTube wormholes: Sondheim teaching masterclasses at the Guildhall School in London. In the sessions, he walks students through some of his most challenging numbers.

There’s something special about watching someone so close to their own material guide performers toward a song’s intent. Sondheim, who is known for his meticulous if not obsessive attention to detail, still leaves room for the students’ own interpretations while giving a rare perspective on the music. It’s one of purest forms of apprenticeship.

“Hold on one second. Now if you’ll take a pause before the word tragedy, it’ll help — take a little catch-breath before the word tragedy so that it will, uhh, contrast with the word pinnacle, which is in the first section. Bless this day...tragedy of life, as opposed to Bless this day tragedy. Isolate the word a little bit,” he tells a student during a rendition of “Getting Married Today” from Company.

Can you imagine? You’re singing one of Sondheim’s songs in front of the man himself and he stops you to tell you where to breathe. I’d just...stop breathing. Happy Birthday, Stephen.