Imagine you are explaining "public domain" to someone who has never heard of it, using "A Dictionary of Music and Musicians" as your example. How would you simplify the concept of why its 1900 publication date makes it freely available in the U.S., highlighting the significance of the "before January 1, 1931" rule?

From the book

Title: La Dolce Vita (1960) by Federico Fellini ← A Dictionary of Music and Musicians ( 1900 ) edited by George Grove → information about this edition related portals : Reference Works Shortcut : DMM 479756 A Dictionary of Music and Musicians 1900 George Grove Preface to Volume 1 Preface to Volume 4 Preface to Index Index to the Four Volumes List of Contributors Catalogue of the Articles by Writer List of Volumes edit Volume 1 - A to IMPROMPTU Volume 2 - IMPROPERIA to PLAIN SONG Volume 3 - PLANCHÉ to SUMER IS ICUMEN IN Volume 4 - SUMER IS ICUMEN IN to ZWISCHENSPIEL This work is in the public…

← Cramer & Co to Davies A Dictionary of Music and Musicians edited by George Grove Davison to Doppio Dorian to Ein' Feste Burg → 1500918 A Dictionary of Music and Musicians — Davison to Doppio George Grove ← Davison to Doppio A Dictionary of Music and Musicians edited by George Grove Dorian to Ein' Feste Burg Eisteddfod to Farandole → 1500921 A Dictionary of Music and Musicians — Dorian to Ein' Feste Burg George Grove ← Dorian to Ein' Feste Burg A Dictionary of Music and Musicians edited by George Grove Eisteddfod to Farandole Farce to Flageolet → 1500924 A Dictionary of Music and Musicians…

← Burden to Carafa A Dictionary of Music and Musicians edited by George Grove Cardarelli to Chapeau Chinois Chapelle to Claudine von Villabella → 1500897 A Dictionary of Music and Musicians — Cardarelli to Chapeau Chinois George Grove ← Cardarelli to Chapeau Chinois A Dictionary of Music and Musicians edited by George Grove Chapelle to Claudine von Villabella Clauss to Conforti → 1500899 A Dictionary of Music and Musicians — Chapelle to Claudine von Villabella George Grove ← Chapelle to Claudine von Villabella A Dictionary of Music and Musicians edited by George Grove Clauss to Conforti…

← Adlgasser, Anton A Dictionary of Music and Musicians edited by George Grove Ad Libitum Adlung, Jacob → sister projects : Wikipedia article From volume 1 of the work. 1502349 A Dictionary of Music and Musicians — Ad Libitum George Grove ​ AD LIBITUM (Lat.). At the pleasure of the performer, as regards time and expression. In the case of arrangements—'with violin or flute ad libitum'—it signifies that the solo instrument may be left out or exchanged at pleasure. ← Acuteness A Dictionary of Music and Musicians edited by George Grove Adagietto Adagio → From volume 1 of the work. 1502314 A…

← A Dictionary of Music and Musicians edited by George Grove Abegg by George Grove Abert, Johann → sister projects : Wikipedia article From volume 4 of the work. 1505260 A Dictionary of Music and Musicians — Abegg George Grove George Grove ​ A BEGG. Schumann's op. 1, published 1831, is entitled 'Thême sur le nom Abegg, varié pour le Pianoforte.' The theme itself is given in vol. iii. p. 408 a . It owed its origin to his introduction to a Miss Meta Abegg, of Mannheim, and was written to please one of his friends who was attached to the lady. The 'Mademoiselle Pauline Comtesse d' Abegg,' to…