Of course you can’t have pop songs without vocals, but when you’re mixing you can have other vocals getting into those pop vibes. To mix pop, a genre that transcends most age groups, most experienced DJs follow a series of guidelines that enable each pop song’s variation to be perfectly in sync with what you want to add to the “DJ plate”.
The problem with mixing voices together is that VERY rarely do they sound well together.
There are DJ that overcome this by adjusting both tracks’ musical keys to match. This creates an unexpectedly good result when introducing a supporting voice to a leading voice, but don’t assume that the same would apply when it comes to two leading voices. This is why there are many variations to making a mix likes this work. Each pop song has a predefined structure that we’ve grown accustomed to.
Most pop songs have a structure: Intro – Verse I – Chorus – Verse II – Chorus – Verse III. Some songs have the Chorus before the verse and some get other sections like Bridge and/or Pre-Chorus.
You can mix Shakira with Beyonce anytime, but just make sure their voices don’t meet for too long. For example, the intro of a song over the chorus section of the song that’s playing and fading out the first track by the time it would reach Verse III will sound much more subtle that bringing both choruses or verses together. If you’re also taking care to avoid redlining and, moreover, use EQs to give the transition even more subtle notes, you’re gonna have a full dancefloor.
Loops of the song you’re bringing to the mix can allow you to introduce even vocals over vocals, as long as you’re not overdoing it. When the Chorus section ends, make steps towards fading the first track out or even using samples to counter a too sudden change.
To mix pop you want to tease the change into your audience by easing in the transition in advance and making a smooth exit.