The 23 separate versions of “Happy Birthday” are done with:

 

Bells

Choir

Concertina

Dulcimer

Flutes

Glockenspiel

Harp

Harpsichord

Hoffner Pick

Hollow Wood

Horns

Kettle Drum

Off Key (for humor)

Orchestra 1

Orchestra 2

Percolator

Piano

Sitar

Sour Notes (a humorously bad guitarist who
                eventually gets it right)

Strings

Toy Piano

Vibes

Violin (pizzicato)