A440 or A4 (also known as the Stuttgart pitch), which has a frequency of 440 Hz, is the musical note of Aabove middle C and serves as a general tuning standard for musical pitch.

The International Organization for Standardization classifies it as ISO 16. Before standardization on 440 Hz, other frequencies were standardized upon. Although not universally accepted, it serves as the audio frequency reference to calibrate acoustic equipment and to tune pianos, violins, and other musical instruments.

https://en.wikipedia.org/wiki/A440_(pitch_standard)

In music, a glissando (Italian: [ɡlisˈsando]; plural: glissandi, abbreviated gliss.) is a glide from one pitch to another
Play (help·info)). It is an Italianized musical term derived from the French glisser, “to glide”. In some contexts, it is distinguished from the continuous portamento. Some colloquial equivalents are slide, sweep (referring to the “discrete glissando” effects on guitar and harp, respectively), bend, smear, rip (for a loud, violent gliss to the beginning of a note),^[1] lip (in jazz terminology, when executed by changing one’s embouchure on a wind instrument),^[2] plop, or falling hail (a glissando on a harp using the back of the fingernails).^[3]

https://en.wikipedia.org/wiki/Glissando