What is the ruling on using programs such as "WhatsApp," "Skype," or "Viber" if the call tones or notification sounds are musical or similar to music, taking into consideration the difficulty of changing the tone on some devices or users' ignorance of how to do so?

It is better not to use programs that contain musical alerts and to replace them with others. However, if it is not possible to change the alert sound, then there is no harm for someone who uses them and promptly mutes the sound of musical instruments when it appears. This is because what is prohibited is the intention to listen to music, not merely hearing it. There is also no harm in calling someone whose phone ringtone is music, if the caller does not intend to listen to it and is in need of making the call.