What is the longest song?

There's no single definitive "longest song" because length can be defined in different ways (duration, number of movements, etc.) and verifiable records are difficult to maintain for all musical works, especially older or less-mainstream ones. However, some contenders for the title, depending on how you measure "longest," include:

• "In C" by Terry Riley: This minimalist composition is often cited as a contender. Its length isn't fixed; performances can last anywhere from 30 minutes to several hours, depending on the performer's interpretation and the number of repetitions. It's less a single song with a defined ending and more a framework for extended improvisation.

• Various Ambient/Drone works: Many artists in the ambient and drone music genres create pieces that can run for hours or even days. These are usually not designed to be listened to in their entirety at once, but rather as an evolving soundscape. Specific examples would be hard to definitively crown as the longest, as lengths can be experimental and potentially indefinite.

• "Organ²/ASLSP" by Jean Michel Jarre: This piece, lasting over two hours, is often cited as one of the longest commercially released pieces of music.

• Conceptual pieces: Some artists have created pieces that extend beyond any practical listening time, perhaps involving extremely slow tempos or generation of sound over years. These often fall more into the realm of conceptual art than traditional music.

The difficulty in declaring a single "longest song" lies in:

• Subjectivity of "song": Some works are more compositional frameworks than traditional songs with verses, choruses, etc.
• Variable length: Many long pieces, particularly in minimalist or ambient styles, don't have fixed durations.
• Lack of central registry: No official body tracks the length of every song ever created.

Ultimately, the title of "longest song" is more a matter of debate and context than a concrete fact. The contenders listed above represent some of the most frequently cited examples of extremely lengthy musical works.