Does he have to denounce it every time he hears musical ring tones from his friends’ mobile phones?
Question

                There is a lot of music everywhere and it is even common in mobile phones, workplaces and public places.  Is the one who listens to it sinning, and does he have to denounce it? Is saying “May Allaah guide you” counted as denouncing? Every time one of my colleagues’ phones rings at work (for example), do I have to denounce him or is it enough to tell him once?.
Praise be to Allah.Firstly: 
Listening to music and 
    putting it on mobile phones and in the workplace is haraam, because the 
    Prophet  (peace and blessings of Allaah be upon him) stated that musical 
    instruments are haraam when he said: “There will be among my ummah people 
    who will regard as permissible zina, silk, alcohol and musical instruments…” 
    Narrated by al-Bukhaari (5590) in a mu’aallaq report. This hadeeth indicates 
    that musical instruments are haraam for two reasons: 
1 – The Prophet’s words 
    “[they] will regard as permissible” clearly indicate that the things 
    mentioned – including musical instruments – are forbidden in sharee’ah, but 
    those people will regard them as permissible. 
2 – Musical instruments are 
    mentioned alongside things that are definitely haraam, namely zina and 
    alcohol; if they were not haraam they would not be mentioned alongside them. 
     
al-Silsilah al-Saheehah 
    by al-Albaani (1/140-141). 
See also question no. 
    5000 
    for the evidence that it is haraam to listen to musical instruments. 
Secondly: 
The sin in listening to 
    musical instruments and other haraam sins applies to the one who listens 
    deliberately, not the one whose ears it reaches without him meaning it to. 
    Al-Manaawi (may Allaah have mercy on him) said: The one who hears it [i.e., 
    musical instruments] should block his ears but if there is haraam 
    entertainment near him he does not have to move, and he is not sinning if he 
    hears it without meaning to. End quote. 
Fayd al-Qadeer 
    (3/355). 
Thirdly: 
The evil must be denounced 
    as much as one is able, with one's hand (by taking action) or with one’s 
    tongue (by speaking out) or in one’s heart (by hating it), because of the 
    report narrated by Muslim (49) from the hadeeth of Abu Sa’eed al-Khudri (may 
    Allaah be pleased with him), that the Prophet  (peace and blessings of 
    Allaah be upon him) said: “Whoever among you sees 
    an evil action, then let him change it with his hand [by taking action]; if 
    he cannot, then with his tongue [by 
    speaking out]; and if he cannot, then with his heart – and that is the 
    weakest of faith.” 
This implies that it must 
    be denounced every time the evil appears and one is able to denounce it, if 
    it happens repeatedly, unless that will cause hardship or lead him to miss 
    out on things that are in his interests, which is more important than 
    denouncing that evil. 
Important: Please see 
    the answer to question no. 96662.
If the one who is 
    denouncing the evil says to the one who is doing it “May Allaah guide you,” 
    this is a kind of denouncing, so long as it is understood as an objection 
    and disapproval of this evil. 
And Allaah knows best.