This film is a Masterpiece with a big M and i'm sure the (few) readers of this my film site have seen it many times.
Everything is PERFECT (besides the poor burning ghost house optical effect and the annoying un-funny farcical cop).
And, one of the things that makes this film Great is Clara Calamai in the role as Carlo's Mother.
One of the Unsung heroes of Profondo Rosso.

Clara Calamai as the sweet old Mother

I've seen this film for surely 40-50 times since the 1980's, first on VHS copies (also the Italian one without subtitles
to get the long Italian version with Hemmings face reflected in the blood at the end and Nicoleta Elmi's lizard), and
then on the DVD's from Anchor Bay and Blue Underground. After all these viewings the film still holds up perfectly
and you can enjoy/delve into the small details of the film and everything looks amazing.
I always enjoys this old lady, what a charisma she exudes, and what strange power. But, i guess i've just taken her
performance for granted and haven't thought that much about her and who she was as an actress.

She's absolutely perfect in the role, and yet i've never heard any discussion about her. Not from Argento, not from fans
and not from the Bonus material makers to DVD or Blu-ray releases through the years. Yes, she's mentioned briefly in
the Commentary track by some Thomas Rostock as a 1930-1940's film actress performing mainly in the then popular
Italian Telefoni Bianchi genre, acting in 1943 Ossessione and then he labels her .... A Fascist Actress. Nice and very
stylish from this dude. She was active in the Italian film industry during the Mussolini years - and long after.
He also talks about the white telephone at the psychic's apartment and the connection to Calamai and her career.
At least he mentions her in the slightly boring commentary track, and something to be thankful for.
(he surely meant to call her a Fascist Era actress, and not a Fascist).

But, even though she died in 1998 it's strange that there's no old interviews with her in any extra stuff, or talk about her
among the genre fans. It would be very, VERY interesting to hear Dario talk about how he chose her, this old famous
italian actress and if the stylish Telefoni Bianchi genre has influenced him in his filmmaking in any way (Dario's Giallo
predecessor Mario Bava had slick telephones in his earlier films). Did they get along? If Tim Lucas, the great Bava
commentary track Maestro, had made the commentary he for sure would've told us a lot about all the actors.

(2022-11-27 note: In the extras to the 4K UHD release more is told about how she got the role)

The Audio Commentary by Thomas Rostock:

Thank You Mr. Rostock .... but i'm NOT BLIND .... you've made a commentary track for blind people for some
unknown reason. I'm sure most viewers has already seen the film when listening to the commentary, and maybe even
seen it many times already, so WHY repeat for 2 hours plus what's happening on the screen? We've seen it, please.
Extremely annoying and boring. He also omits telling us about some of the actors.

He misses mentioning the window scene borrowed from "Sette Scialli di Seta Gialla" (Seven Shawls of Yellow Silk/The
Crimes of the Black Cat", but mentions the influence from painter Edward Hopper (the bar at the Turin square), The
Spiral Staircase from 1946 by Robert Siodmak (eye in the closet) and from the filmmaker Antonioni.
Also, i didn't know that the boyfriend of Carlo were played by a woman, Geraldine Hooper (and Gabriele Lavia's
girlfriend at the time according to Daria Nicolodi)

Arrow Video 2016 Blu-ray Turnable sleeve

What about Daria Nicolodi constantly bashing Dario in every interview on every DVD or Blu-ray disc ?

In the extras on this disc there's an interview with Daria Nicolodi and she's very interesting to listen to as usual.
Obviously she co-scripted this film without being credited, then she scripted Suspiria and i'm sure Dario's post-1987
films would've been much, MUCH better if she had written the scripts, including the third awful Mother film.
Aaaah, it's a pity they broke up after 12-13 years together, Daria was there during The Golden Years of Argento.

But, for about a decade now Daria has attacked Dario in her interviews. A Bitter but Good-Humoured woman?
He tried to kill her during the filming of Opera (bullet through the eye scene), Suspiria and Deep Red were really
that good because of her scriptwork and presence, he's a tyrant and a nasty human being etc etc.
But in this interview from the Deep Red Blu-ray extras she really goes too far. OK, she tells the nasty things about
him with a smile, and i'm not sure if this constant bashing is a long ongoing joke or not ?
Dario is terrible with actors and was nasty to poor David Hemmings, Dario don't want to give credit to anyone else
besides himself, he's egocentric, narcissistic and a total hypocondriac .... and nastier, Dario can't sleep with a woman
in a bed, don't want to be touched. Wow, that's just so .... LOW. But, it may be a joke that Dario's in on, who knows?

US Blue Underground DVD

The Story ? No, no, everyone of you has seen this film already as it's a giallo horror classic, so i won't bore you much.
A lovely German Psychic (Macha Meril) is killed by a psychopath and a British (?) pianist played nicely by David "Blow
Up - Barbarella" Hemmings starts to investigate by himself. The Hallway with the paintings scene must be one of the most
ingenious in the history of Horror. The killings by the psycho are gruesome and effects were created by Carlo Rambaldi.
In the Amanda Righetti (Giuliana Calandra) murder scene the eye in the closet is a homage to The Spiral Staircase, 1946,
and Argento used the eyes again in Suspiria (but more demonic then in the eyes outside of window scene) and then again
in Inferno (demonic again and painted by Mario Bava in the Irene Miracle chase scene).

Some thoughts: In the beginning we the viewers, not David Hemmings, get to see that the killer uses a Kajal pencil around
the eyes .... who in the film has kajal made make-up around the eyes? There are only 2.
Dario is playing with open hands and later also let us see the killer for some second. So, the killer is no big mystery to us.
Why is the killer leaving Marc Daly (David Hemmings) unconscious in the Ghost house and not killing him before setting
the house on fire, when she has bestially murdered all the others ? (..... OK, if so, then Daria wouldn't have rescued him).

Fulvio Mingozzi is Not a cab driver in this film, as in Suspiria when driving Jessica Harper to the Ballet Academy in Freiburg,
or as in Inferno when driving Eleonora Giorgi to the Library in Rome, or as in Phenomena when driving Jennifer Connelly
and Daria Nicolodi to the school, in Deep Red he's a police agent.
We've 2 creepy kids in this one, red-haired Nicoleta Elmi and Jacopo Mariani as the boy, also in Suspiria with the witches

widescreen 2.35:1, italian audio DTS-HD MA 5.1 or mono with english subs, or english and italian hybrid mono audio
Extras: introduction by Claudio Simonetti from Goblin, audio commentary with Argento expert Thomas Rostock, Profondo
Giallo Video Essay by Michael MacKenzie (33 min), Rosso recollections: Director Dario Argento discusses his most
celebrated giallo (12 min, in italian with english subs), The Lady in Red: Daria Nicolodi remembers Profondo Rosso (19 min,
in italian with english subs), Music to Murder for: Interview with Goblin's Claudio Simonetti (14 min), From Celluloid to
Shop: Luigi Cozzi in the Profondo Rosso shop (14 min, in italian with english subs), Italian trailer

My favourite extras were: The Dario and Daria interview. Great to hear them tell anecdotes, with the exception of Daria's
unneccessary stabbings at Dario. Argento seems to be milder and friendlier these days and i could listen to him telling us
about filmmaking and whatever for hours. It would be nice to have ALL of the extra material to Deep Red gathered on
one disc, but i guess you will have to buy the Blue Underground disc also and maybe some other company's releases