Does [m] sound influence [ɑ] sound?

[eipjoo]

. . . calm . . . heart . . . heart . . . half . . . [audio source]

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The first [ɑ] sound in calm seems to be made at noticeably nearer the middle [IPA] than the others. Am I
hearing right? If yes, is it because of [m] sound that is made in front?

[5jj]

f yes, is it because of [m] sound that is made in front?

No. Speakers of four very different dialects were saying those words. If you want to discuss the pronunciation of the vowels in 'half', 'heart' and 'calm', you need to have recordings of one person saying all three words. I have the same sound in the onset of the vowel in all three word, but the vowel of 'heart' begins to differ from that of 'calm' and 'half' as I approach the following approximant. The final consonant makes no difference to the vowel.

[raindoctor]

It is often said that low vowels are produced with open jaw. One can produce low vowels with close jaw. The trick is to cup the tongue. In other words, one can produce vowels just with tongue action alone: cupping, arching, bunching, etc. Different languages use different settings for sake of articulatory ease. Just because one particular setting is easy for speakers of a particular dialect; it does not mean that such a setting is easy for everyone else. This has to do with how neuromuscular system is trained by their first language/dialect, thereby becoming 'natural'.

[5jj]

It is often said that low vowels are produced with open jaw. etc

Does this have any relevance to the original question?

[raindoctor]

Does this have any relevance to the original question?

Yes, figure it out, as you are the expert here.

[5jj]

Well, I am not an expert on phonetics, and have never claimed to be. And, I do not see the relevance of your post to the original question, which is why I asked about it. So, could you please explain for the non-experts how that answers eijpoo's question?