Those so-called "nasheed concerts" aren't any different than musical concerts! They do quite an injustice to nasheed. Nasheed is meant to be a vocal, harmonious or melodious praise of Allah, Islam, blessings on Prophets and their families, or anything that promotes or talks about Islam. THEY SHOULD HAVE NO MUSIC! At all! Nasheed and music should be two separate things! If nasheed has music, it is considered impermissible as nasheed. Astaghfirullah.
A Muslim may engage in nasheed. Indeed, why should we abstain from praising Allah, our Lord? We should stay away from nasheed with music in it. They shouldn't even be considered nasheed, as their intention cannot be truly sincere in its praise if it involves music. It's like hurting and helping yourself at the same time.
There are certain halal drums that are used in nasheed, but other than those, no music, or imitation of music should be used in the nasheed - otherwise it cannot be considered so! However, harmony of the voice is halal, and is often used in many creative ways in nasheed.
Examples of music-free nasheed can be any nasheed by Dawud Ali Wharnsby, "La Ilaha Illallah" by Mishary Rashid Al-Afasy, or "Allahu" by Labbayk.
The proper nasheeds do have benefit. I recall that the Prophet (SAW) would sit in a circle with some companions, and he would have one of them stand up (I don't think I remember his name) and sing a nasheed by himself before having him sit down again to turn to another companion to read Qur'an. Allah forgive me if I have recalled incorrectly and written any inaccuracies, astaghfirullah.
I hope this clears it up! ^ ^