Firstly: 

Making one’s voice beautiful when reciting Qur’aan is something good and there is nothing wrong with it; rather this is part of the teaching of the Prophet (peace and blessings of Allaah be upon him). 

It was narrated that al-Bara’ (may Allaah be pleased with him) said: “I heard the Prophet (peace and blessings of Allaah be upon him) reciting Wa’l-teeni wa’l-zaytoon in ‘Isha prayer, and I never heard anyone with a more beautiful voice (or recitation) than his.” 

Narrated by al-Bukhaari, 735; Muslim, 464 

And the Prophet (peace and blessings of Allaah be upon him) praised the recitation of Abu Moosa al-Ash’ari, who had a melodious voice. But the kind of making the voice beautiful which is encouraged should not distort the meaning of the words and it should not resemble the way that the evildoers sing songs. 

It was narrated that Abu Moosa said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said to Abu Moosa, “If only you had seen me when I was listening to you last night, you have been given a beautiful voice like that of Dawood.”  

Narrated by al-Bukhaari, 4761; Muslim, 793; this version narrated by Muslim 

Al-Nawawi said: 

Al-Qaadi said: The scholars are unanimously agreed that it is mustahabb to make one's voice beautiful when reciting Qur’aan and to recite properly (tarteel). Abu ‘Ubayd said: The ahaadeeth narrated concerning that are to be understood as meaning that it should be done with solemnity and feeling. He said, But they differed with regard to reciting it with a tune. Maalik and the majority regarded that as makrooh because that is contrary to the purpose for which the Qur’aan was revealed, whichis to be recited with humility and understanding. Abu Haneefah and a group among the Salaf regarded it as permissible because of the ahaadeeth and because that is a means of softening people’s hearts, provoking fear and making people receptive towards listening to it. 

I say: al-Shaafa’i said in one place, I dislike reciting Qur’aan with a tune; and elsewhere he said, I do not dislike it. Our companions said: there is no contradiction in this case, rather it has to do with two different situations. When he said that he disliked it, he meant if it was excessively elongated and the meanings of the words were changed by adding or taking away or elongating something that is not to be elongated, etc.; and when he said that it was permissible, he meant if it does not change the meaning of the words. And Allaah knows best. 

Sharh Muslim, 6/80 

Secondly: 

With regard to what your imam does, putting his hand on his forehead and saying Yaa Hayyu, Yaa Qayyoom seven times, there is no basis in sharee’ah for doing this, and it is not in Saheeh Muslim or any other book of saheeh Sunnah. It is a reprehensible bid’ah (innovation) and you have to advise him to stop doing that and explain the shar’i ruling on innovated forms of dhikr. 

With regard to praying behind this imam: it is permissible but it is preferable if you can look for an imam who will establish the Sunnah and teach it to you, because there is the fear that some of the worshippers may be influenced by him and may imitate him and spread his bid’ah. But before doing that, do not forget to advise him and teach him the correct Sunnah for dhikr in particular and for worship in general. Then if he insists on his bid’ah, there is nothing wrong with you taking action to prevent him from leading the prayer. 

The scholars of the Standing Committee said: 

As for praying behind those who follow innovation, if their innovation involves shirk, such as calling upon someone other than Allaah, or making vows to someone other than Allaah, or believing that their shaykhs have characteristics which belong to no one but Allaah, such as having complete knowledge or knowledge of the unseen or influence over the universe, then it is not correct to pray behind them. But if their bid’ah does not involve shirk, such as reciting dhikr that was narrated from the Prophet (peace and blessings of Allaah be upon him) but in unison and swaying, then prayers offered behind them are valid, but the Muslim should look for an imam to pray behind who is not an innovator, because that will bring him a greater reward and is farther removed from evil. 

And Allaah is the Source of Strength. May Allaah send blessings and peace upon our Prophet Muhammad and his family and companions. 

Fataawa al-Lajnah al-Daa’imah, 7/353

 And Allaah knows best.