I first heard about the existence of these acetates from Bill in May 2021, and I and my fellow compilers---Armando Cesari, Vince Di Placido, and Carmel Parisi---were simply over the moon when we started receiving file after digital file from Bill shortly after that. For the first time, we were able to hear, among other things, Lanza's magnificent  first recording of "My Destiny," the original (pre-edit) first take of "Beloved" from Lanza's May 1953 remake session of the song, the Finale from Marta featured in The Great Caruso in its original form---without all the coughing!---the full version of "Una furtiva lagrima" from That Midnight Kiss, "Celeste Aida" from the same film but this time with its previously discarded recitative, a longer extract of the Rigoletto Quartet recorded for The Great Caruso, a complete version of the Addio alla Madre from Because You're Mine that is superior to the take featured on the 1998 Rhino CD Mario Lanza at MGM, and many other treasures.

Major sound restoration was necessary, as many of the recordings were severely scratched, and/or suffered from extensive surface noise. Sepia Records' sound engineer, Robin Cherry, has performed miracles on many of them, but allowances still need to be made for some of the recordings. I doubt that anyone who loves Lanza will complain, though, as where else can one find a restored version of, say, the 1945 live radio broadcast of "The House on the Hill," or the 1959 "Nocturne"---with the tenor's voice now front and centre (exactly as recorded in the studio and not blighted by incompetent posthumous mixing)?

Here is the full track listing:

1 The House on the Hill  (Charles)
Live CBS radio broadcast from Liederkranz Hall, New York City, 7 November 1945.                  
2 I Know, I Know, I Know (Kaper-Russell)  [original film acetate---and it sounds glorious]
MGM Studios, Los Angeles, 1 December 1948.         
3 O Holy Night (Adam) [original acetate]
Republic Studios, Los Angeles, 29 May 1950.                                                                    
4 The Lord’s Prayer (Malotte) [with organ only] [original film acetate]
MGM Studios, 2 August 1951.                                                   
5 Deep in My Heart, Dear (from The Student Prince) (Romberg-Donnelly) [outtake]
MGM Studios, 12 August 1952. With Ann Blyth, soprano. 
6 My Destiny  (Brodszky-Cahn) [outtake--superior to the version featured in the film]
Warner Bros. Studios, Los Angeles, 7 July 1955. Jakob Gimpel, pianist.                         
7 Serenade (from the film Serenade) (Brodszky-Cahn)  [original film acetate, with previously unheard orchestral intro]    Note: This is the soft "Mexico" version of the song.
Warner Bros. Studios, 26 August 1955.       
8 Ave Maria (Bach-Gounod) [original film acetate]
MGM Studios, 11 August 1950. With Jacqueline Allen, soprano.
9 L’elisir d’amore: Una furtiva lagrima (Donizetti-Romani) [full version] 
MGM Studios, 9 December 1948. José Iturbi, pianist.                
10 Carmen: Flower Song (“La fleur que tu m’avais jetée”) (Bizet-Meilhac-Halévy) [full version; sounds better than in Toast of New Orleans]
MGM Studios, 6 December 1949. Jakob Gimpel, pianist.                                   
11 Aida: Celeste Aida (Verdi-Ghislanzoni) [full version]
MGM Studios, 9 December 1948. José Iturbi, conductor; MGM Studio Orchestra.          
12 Aida: O terra addio (Verdi-Ghislanzoni) [original film acetate; glorious!]
MGM Studios, 18 August 1950. With Dorothy Kirsten, soprano, and Blanche Thebom, mezzo-soprano. 
13 Rigoletto: È  il sol dell’anima (Verdi-Piave) [rehearsal]
MGM Studios, 28 August 1950. With Jarmila Novotná, soprano. 
14 Rigoletto: È  il sol dell’anima (Verdi-Piave) [outtake]
See #13 for recording details.  
15 Rigoletto: Addio! Addio! (Verdi-Piave)  [original film acetate]                    
MGM Studios, 24 November 1951. With Peggy Bonini, soprano.  
16 Rigoletto: La donna è mobile (Verdi-Piave) [live performance]
Performed at Massey Hall, Toronto, 5 March 1948.                         
17 Rigoletto: Quartet (“Bella figlia dell’amore”) (Verdi-Piave) [New extended version]
MGM Studios, 22 August 1950. With Giuseppe Valdengo, baritone; B. Thebom; Olive May Beach, soprano.       
18 Lucia di Lammermoor: Sextet (“Chi mi frena in tal momento?”) (Donizetti-Cammarano) [film acetate with a somewhat different mix from what we hear in the movie; Mario's voice is more forward]
MGM Studios, 23 August 1950. With D. Kirsten; G. Valdengo; B. Thebom; Nicola Moscona, bass; Gilbert Russell, tenor. 
19 Marta: Finale (von Flotow-Riese) [original film acetate]
MGM Studios, 22 August 1950. With D. Kirsten, N. Moscona, and B. Thebom. 
20 La bohème: Che gelida manina   (Puccini-Giacosa-Illica) [original film acetate]
MGM Studios, 29 August 1950. P.H. Adler, conductor; MGM Studio Orchestra.      
21 Cavalleria rusticana: Addio alla Madre (Mascagni, Targioni-Tozzetti, Menasci) [New extended version]
MGM Studios, 10 November 1951. With Katherine Hilgenberg, contralto; and P. Bonini. John Green, conductor; MGM Studio Orchestra.
22 Il trovatore: Di quella pira  (Verdi-Cammarano) [original film acetate]
Warner Bros. Studios, 13 July 1955.  Ray Heindorf, conductor; Warner Bros. Studio Orchestra.              
BONUS TRACKS                                       
23 Ave Maria (Schubert) [original film acetate; superior sound to previous reproductions]
Warner Bros. Studios, 18 August 1955. Jakob Gimpel, pianist.
24 Pour un Baiser  (Tosti-Doncieux) 
Cinecittà Studios, Rome, June 1959.                                                                             
25 Love Me Tonight  (from The Vagabond King) (Friml-Hooker-Post) [original "raw" acetate]
Cinecittà Studios, July 1959.  C. Callinicos, conductor; RCA Italiana Orchestra.   
26 Nocturne (from The Vagabond King) (Friml-Hooker-Post) [original "raw" acetate]
Cinecittà Studios, July 1959. C. Callinicos, conductor; RCA Italiana Orchestra.    
27 Beloved  [the unedited first take from the May 1953 remake session]
MGM Studios, 20 May 1953. C. Callinicos, conductor; MGM Studio Orchestra.
28 La Danza (Rossini)   [original film acetate]       
MGM Studios, 7 August 1950. Irving Aaronson, pianist.               

I should add that the CD booklet is stunningly presented, and includes comprehensive notes and rare photos.

UPDATE (23 March): This CD is now in stock at Sepia Records in London and can be ordered here. The price, including postage, is £7.99 for the UK; £9.99 for those elsewhere in Europe; and £10.99 (= US$14.60) for the rest of the world. 
For those in the US only, the CD is now in stock at the Mario Lanza Museum in Philadelphia. Bill Ronayne, President of the Mario Lanza Institute, writes: "The CD is $12 + $5 Shipping & Handling. Checks should be made out to Mario Lanza Institute and sent to Mario Lanza Institute 1214 Reed Street Philadelphia, PA 19147. For credit card orders, more information or if you're ordering more than one CD, call 215-238-9691."
It is also currently available for pre-order from Amazon, with a scheduled release date of April 1. 

Vincent Di Placido has created a beautiful promotional video for this CD (see below). 

A case in point is the magnificent 1950 recording of the Improvviso ("Un dì all’azzurro spazio") from Giordano's Andrea Chénier, which has never sounded more vibrant. There are numerous other surprises too, particularly among the lesser known (or, in some quarters, less appreciated) late-career gems such as "Just We Two" (from Lanza's 1959 remake of The Student Prince) and the "Drinking Song" from The Vagabond King, both of which now feature a more vital-sounding tenor than heard on previous releases. 
Here is a description of the CD's contents from my liner notes:

"This CD celebrates Mario Lanza’s centenary with a collection spanning the tenor’s entire professional career, from his first radio broadcasts to a quartet of studio gems from the last months of his brief but indelible life. Four of the selections are making their first appearance on a commercial CD; they include a spectacular rehearsal of “Some Day” and extended versions from Lanza’s own archives of material recorded for The Great Caruso. Other rarities include live performances of duets from The Student Prince and Verdi’s Otello. Throughout the CD, Lanza’s celebrated versatility is on full display, with every musical genre in which he excelled represented here." 

UPDATE (12 June 2021): The Immortal Voice of Mario Lanza: A Centennial Celebration is now available directly from Sepia Records for immediate delivery, and will be released in the US on July 16. Here is the Amazon US link for preorders. The Mario Lanza Institute and Museum is also offering this CD (and all of the previous Lanza CDs on the Sepia Records label).

Here is the full track list of the CD:

THE IMMORTAL VOICE OF MARIO LANZA:
A CENTENNIAL CELEBRATION
1 Cavalleria Rusticana: Brindisi  
Recorded August 23, 1950 [longer version of the extract featured in The Great Caruso]                      
2 Ergo Bibamus  
Recorded August 7, 1952  [acetate recorded for the film The Student Prince]                                             
3 Just We Two (from The Student Prince)  [with Norma Giusti, soprano]
Recorded April 1959
4 If I Loved You (from Carousel) 
Recorded February 15, 1952     [with spoken introduction by Lanza]           
5 Long Ago (and Far Away) 
Recorded July 13, 1951                        
6 Some Day (from The Vagabond King) 
Recorded October 28, 1954   [previously unreleased television rehearsal]                      
7 Trees      
Recorded November 20, 1951             
8 The Virgin’s Slumber Song
Recorded May 29, 1950                                
9 Neapolitan Love Song (from Princess Pat) 
Recorded November 29, 1951 
10 La Spagnola 
Recorded May 9, 1952                         
11 Core ’ngrato 
Recorded May 5, 1949                                     
12 Marechiare 
Recorded August 9, 1950 [complete (one-verse) film take for The Great Caruso]                                              
13 Torna a Surriento 
Recorded June 30, 1955                                     
14 Santa Lucia Luntana 
Recorded December 1958                                        
15 L’Alba Separa dalla Luce l’Ombra 
Recorded at June 1959                                    
16 Pagliacci: Vesti la giubba 
Recorded September 1958                                          
17 Andrea Chénier: Improvviso (Un dì all’azzurro spazio) 
Recorded May 18, 1950
18 Tosca: E lucevan le stelle      
Recorded July 22, 1950   [a much longer version of the recording featured in snippet form in The Great Caruso)    19 Otello: Già nella notte densa (Verdi-Boito)  [with Jean Tennyson, soprano]
Live CBS broadcast on November 14, 1945
BONUS TRACKS
20 Golden Days (from The Student Prince)  [with Robert Weede, baritone] 
Live CBS broadcast on February 20, 1946
21 Summertime in Heidelberg 
Recorded April 1959 [revelatory solo version taken from Lanza's private acetate] 
22 Drinking Song (from The Vagabond King)         
Recorded July 1959   
23 Without a Song 
Recorded August 14, 1951​​

Vincent Di Placido has just uploaded a documentary he has made about another pivotal moment in Mario Lanza's career: the tenor's triumphant return to live performing after a long absence from the concert stage and a two-year period of professional turmoil.

Vince's documentary is partly based on my article Confounding the Enemy, but he takes my essay to a whole new level with his superb (and often moving) editing of audio and visuals, while also providing a powerful introduction that provides genuine historical context to this event. 

​A must watch!  

Vince Di Placido is an indispensable member of the online Lanza community---as highly regarded for his superb video presentations of Lanza's legacy as he is for his musical knowledge and the intelligence he brings to discussions on the tenor.

All of these qualities are to the fore in his latest video: a magnificent in-depth tribute to the great Mario! album of Neapolitan songs that Lanza recorded in December 1958.    

The commercial recordings on this 74-minute CD were sourced from the best-available pre-1963 vinyl releases that Vince Di Placido and I could find, while the two non-commercial recordings featured here—--"Granada" and "Because"—--were drawn, respectively, from the optical track of a late 1950s film print of Because You're Mine and a 1959 RAI radio programme ("La Mia Vita per il Canto"). All have been lovingly remastered by Sepia's resident sound engineer, Robin Cherry.
The CD also includes a generously filled booklet of detailed liner notes and several rare photos. 
Mario Lanza: Classics is available from 7 February 2020 at Amazon and all the other usual online outlets. This is the link for Amazon UK and here is the US Amazon link. ​
The following is a description of the CD, taken directly from my liner notes:

This CD brings together Lanza’s most popular recordings, including his three million-selling singles (all making their first appearance on this label), his Top 20 chart successes in both the United States and the United Kingdom, and the highlights from his two best-selling albums, The Great Caruso and The Student Prince. It also includes a representative sampling of the tenor at his vocal and stylistic zenith in multiple genres, with definitive renditions of everything from an Edwardian parlour song (“Because”) to five Neapolitan classics. As such, this CD serves as both the perfect introduction to the art and voice of Mario Lanza and—for his existing admirers—an unusually convenient compilation of many of his greatest recordings. 

MARIO LANZA: CLASSICS
1   Granada   (Lara)    (Lanza's 3rd and final version, recorded in 1951)        
​2   Be My Love (Brodszky-Cahn)                                                                                                      
3   Because     (d’Hardelot-Teschemacher)                                                                                             
4   The Loveliest Night of the Year (Aaronson-Webster-after Rosas)                                                  
5   Some Day (Friml-Hooker)                                                                                                            
6   The Lord’s Prayer (Malotte)    (RCA)                                                                                                     
7   Because You’re Mine (Brodszky-Cahn)   (RCA)                                                                                      
8   Serenade (from The Student Prince) (Romberg-Donnelly-Webster)  (MGM)                                            
9   Drink! Drink! Drink! (Romberg-Donnelly)   (MGM)                                                                                    
10  Beloved     (Brodszky-Webster)     (1953 version)
11  Mamma Mia, Che Vò Sapé? (Nutile-Russo)  (RCA)                                                                                
12  Voce ’e Notte (De Curtis-Nicolardi)                                                                             
13  Canta pe’ Mme! (De Curtis-Bovio)    (RCA)                                                                        
14  ’Na Sera ’e Maggio (Cioffi-Pisano)   (RCA)                                                                      
15  Sadko (adapted): Song of India (Rimsky-Korsakov; adapted Mercer)                                        
16  Tosca: Recondita armonia (Puccini-Giacosa-Illica)   (RCA)                                                                    
17  La bohème: Che gelida manina (Puccini-Giacosa-Illica)  (RCA)
18  Martha: M’apparì (Von Flotow-Riese)                                                                                             
19  Tosca: E lucevan le stelle (Puccini-Giacosa-Illica)   (RCA)                                                                    
BONUS TRACKS
20  Ave Maria (Bach-Gounod)   (RCA)                                                                                                     
21  Serenade (Drigo)   (RCA)                                                                                                                      
22  Tell Me, Oh Blue Blue Sky (Giannini-Flaster)   (Live from the Royal Albert Hall)                                          23  Passione (Tagliaferri-Valente-Bovio)                                                                            ​

I'm delighted to report that London-based Sepia Records will soon be releasing another Mario Lanza CD compilation: its sixth (!) in three years. 

Titled Poetry and Passion, this CD differs from the previous five Sepia compilations in that it doesn't focus on one particular musical genre. Instead, it offers examples of Lanza in top form in every genre in which he excelled: opera, operetta, musical theatre, Neapolitan song, and popular song. An eclectic compilation, to be sure, but one that's full of surprises and consistently rewarding, delivering exactly what its title promises.

As with the previous five Sepia releases, the CD was compiled (for love, not money) by Armando Cesari, Vince Di Placido, Carmel Parisi, Lee Ann Cafferata and yours truly, and expertly remastered by Robin Cherry. Indeed, many of the recordings have never sounded better, despite being sourced from an assortment of vinyl, private tapes and acetates. The same care has gone into the CD booklet, which is beautifully presented with copious notes and several rare photos. 
​
Poetry and Passion is now available directly (and economically for those outside of the UK) from Sepia Records, and will be released by Amazon and other online sellers on February 9, 2018. 

UPDATE (5 Feb 2018): Lindsay Perigo has posted this glowing review of the CD on his web site.

MARIO LANZA: POETRY AND PASSION
1   Earthbound (Taylor-Richardson-Musel) Recorded 10 August 1956
2   Wonder Why (Brodszky-Cahn) 21 August 1951
3   The Bayou Lullaby (Brodszky-Cahn) 29 June 1950
4   Beautiful Love (King-Young-Van Alstyne-Gillespie) 24 April 1952
5   Tell Me Tonight (Spoliansky-Eyton) 15 February 1952
6   The Rosary (Nevin-Rogers) 23 August 1951
7   The Song Angels Sing (Aaronson-Webster, adapted from Brahms) 24 July 1952
8   The Thrill Is Gone (Henderson-Brown) 29 November 1951
9   My Destiny (Brodszky-Cahn) 21 July 1955    [Introduced by Lanza]
10  Younger Than Springtime (Rodgers-Hammerstein) 7 November 1957
11  Thoughts Will Come Back to Me (Romberg-Donnelly) April 1959
12  Nocturne (Friml-Hooker-Post) July 1959
13  Lygia (Rózsa-Webster) 16 December 1951
14  Come Prima (For the First Time) (Di Paola-Taccani-Ram) September 1958
15  ¡Ay, ay, ay! (Freire) 3 December 1951 
16  Maria Marí’ (Di Capua-Russo) December 1958 
17  Ave Maria (Schubert) 18 August 1955    [film outtake with piano]
18  L’Arlesiana: È la solita storia (Cilea-Marenco) 16 Jan. 1958  [live: Royal Albert Hall]
19  Otello: Niun mi tema (Verdi-Boito) September 1958
BONUS TRACKS
20  Pagliacci: Un tal gioco (Leoncavallo) May 1952  [private recording]
21  Andrea Chénier: Un dì all’azzurro spazio (Giordano-Illica) April 1952  [private recording]
22  I’m Falling in Love with Someone (Herbert-Young) 18 January 1958 [live performance: British TV]
23  Only a Rose (Friml-Hooker-Post) July 1959  ["Raw" acetate: a revelation!]