There is a big difference in opera and Broadway musicals. Here is a list of almost all operas beginning with the letter P:
Pagliacci
Pan Voyevoda
Panurge
Patience and Sarah
Pelléas et Mélisande
La Périchole
Peter Grimes
Pikovaya dama
Pir vo vremya chumy
Poliuto
Porgy and Bess
Le portrait de Manon
Príhody lisky Bystrousky
Prométhée
Pskovityanka
And the following is a list of all musicals with the letter P:
Pacific 1860, West End musical (1946) by Noel Coward, starring Mary Martin
Pacific Overtures, Broadway musical (1976) with music and lyrics by Stephen Sondheim
Paint Your Wagon, Broadway musical (1951) with book and lyrics by Alan Jay Lerner and music by Frederick Loewe (Lerner and Loewe), filmed by Paramount in 1969
The Pajama Game (1954), book by George Abbott and Richard Bissell, music and lyrics by Richard Adler and Jerry Ross; notable songs: "Steam Heat", "Hernando's Hideaway"
Pal Joey, Broadway musical (1940), lyrics: Lorenz Hart, music: Richard Rodgers. Broadway production opened on December 25, 1940 at the Ethel Barrymore Theatre and ran for 374 performances. Filmed by Columbia Pictures in 1957. Notable song: Bewitched, Bothered, and Bewildered
Panama Hattie, Broadway musical (1940) with music and lyrics by Cole Porter, filmed by MGM in 1943
Parade, (1998) Broadway musical with music and lyrics by Jason Robert Brown; book by Alfred Uhry.
Paris 1928 Cole Porter musicals
Paris 2003 Australian musical
Passing Strange, (2008) Broadway musical with lyrics and book by Stew, music by Stew and Heidi Rodewald
Passion, Broadway musical (1994) with music and lyrics by Stephen Sondheim
The Phantom of the Opera West End musical' (1986) (Andrew Lloyd Webber) Notable songs: "The Phantom of the Opera", "The Music of the Night", "All I Ask of You", currently the longest runner on Broadway.
Passion Flower Hotel, West End musical (1965)
Perchance to Dream, West End musical (1945) (Lyrics, Music and Book by Ivor Novello)
Pennies from Heaven, MGM film (1981), various composers and lyricists.
Le Petit Prince, a French musical by French musical composer Richard Cocciante played at the Casino de Paris from October 2002 to January 2003
Peter Pan, Broadway musical (1950), music and lyrics: Leonard Bernstein.
Peter Pan, Walt Disney film (1953), music: Frank Churchill, Sammy Fain, Oliver Wallace, lyrics: Sammy Cahn, Winston Hibler, Jack Lawrence, Ed Penner, Ted Sears.
Peter Pan, Broadway musical (1954), music: Mark Charlap, Jule Styne, lyrics: Betty Comden, Adolph Green, Carolyn Leigh.
Pete's Dragon, Walt Disney film (1977), songs by Al Kasha and Joel Hirschhorn; notable song: "Candle on the Water"
Phi-Phi, French musical (1918)
Pickwick, West End musical (1963) with music by Cyril Ornadel, produced on Broadway in 1965
Piece produced by Playing Pretend Productions, music and lyrics written by Scott Alan, book written by Tara Smith
"Pied Piper Of Hamelin, The. 1984 Los Angeles Musical. By Richard Jarboe and Harvey Shields
Pink Floyd The Wall (1982)
Pinocchio 1940 disney film
Pins and Needles, Broadway revue (1937) with songs by Harold Rome, produced by the International Ladies Garment Workers Union
Pipe Dream, Broadway musical (1955) with book and lyrics by Oscar Hammerstein II, music by Richard Rodgers
Pippin, Broadway musical (1972), music and lyrics: Stephen Schwartz.
The Pirate Queen 2007 planned Broadway run, by Claude-Michel Schönberg and Alain Boublil
Plain and Fancy, Broadway musical (1955) with music by Albert Hague and lyrics by Arnold Horwitt
Platinum, Broadway musical (1979), music: Gary William Friedman, lyrics: Will Holt, starring Alexis Smith
Play On, Broadway musical (1997) adapted from William Shakespeare's Twelfth Night, with music by Duke Ellington
La Plume de Ma Tante, French revue, produced on Broadway in 1958, written, devised, and directed by Robert Dhery, music by Gérard Calvi, English lyrics by Ross Parker
Pocahontas, Walt Disney film (1995), music: Alan Menken, lyrics: Stephen Schwartz.
Polonaise 1945
Pomme d'amour film 1932
Pom-Pom 1916
Poor Little Rich Girl film 1936
Popeye, Paramount film (1980), music and lyrics: Harry Nilsson, Sammy Lerner.
Porgy and Bess, Broadway opera (1935) music: George Gershwin; lyrics: DuBose Heyward, Ira Gershwin.
Portofino, Broadway musical (1958), a famous fiasco that closed after 3 performances
Pot O'Gold film 1940
Pride and Prejudice, by Bernard J. Taylor, studio concept recording 1993 with Peter Karrie, Claire Moore (singer), and other West End musical stars. World premiere at the Madison Theare, Peoria, Illinois (1993)
The Producers, Broadway musical (2001) (Mel Brooks) Was first released as a film, yet did not have the success that it was noted for when moved to Broadway Notable songs: "Springtime for Hitler" and "I Want to be a Producer"
Promenade (1969), off-Broadway absurdist musical by Maria Irene Fornes, with music by Rev. Al