I have spoken about glide affrication before - the process that makes "y" sound like "j" and "w" sound like "v." But did you know there's also affrication of stops in English? It makes "t" sound like "ts" and "d" sound like "dz." It can also make "k" sound like "khhh" and "p" like "pf".
What causes stop affrication? Well, it's a natural result of 'lengthening' a stop. A stop, by definition, is when a bunch of air builds up behind part of your mouth and is then suddenly released, causing a 'pop' sound. How can you lengthen this release of air? You can't, but you can continue pushing air from the lungs through, which causes a friction - hence affriccation. You can think of it like a stop combined with a fricative that's formed at the same part of the mouth.
Wells's Accents of English associates this sort of affrication with Cockney English speakers. But I've found examples of it across different dialectal regions. Like S-retraction, it seems to be a change that has developed multiple times in different places.
From New York City - musicians as distinct as Latin pop singer Ricky Martin and j-pop singer Utada Hikaru have d-affrication. Utada's example is especially song. (I recommend headphones to be able to hear the frication more clearly compared to the music.)
Her lips are dzevil red
The dzaily things
Billy Joel also has t-affrication at the end of a word:
If that's what it's all abouts, mama if that's movin' up, then I'm movin' outs... mmm I'm movin' outs.
Over in California, Disney Channel child actress Emily Osment (from Hannah Montana) has some dramatic d-affrication:
Dzoesn't matter what you say, I'm knockin' you dzown, dzown, dzown
And in Texas, fellow Disney Channel alum and singer Demi Lovato has some d-affrication, though not consistently (audio slowed down):
Are you kidding me? I'm so not a dziva
In the Midwest, the lead singer of the rock band Fallout Boy, Patrick Stump, frequently uses affrication in his music. Sometimes it's from lengthening the consonant. Compare the 'k' in 'mistakhhh' to the simply released 'k' in 'take':
And just one mistakhh is all it will take
Stump also seems to display a curious case of p-affrication where 'proof' sounds like 'pfroof' (at least, the official lyrics are 'proof'). This has led multiple fans and lyrics sites to mistakenly hear the lyric as "frozen fruit."
And here's the frozen pfroof
Some of these examples seem to result from attempting to 'extend' a stop consonant (Stump's "mistakkhe"). Some might result due to being near a front vowel, like Demi Lovato's "dziva." This sort of affrication before front vowels also happens in Canadian French (audio slowed down):
La fondation Celine Dzion
A similar thing happens in Russian. In Russian, oral stops that are palatalized (pronounced with the tongue raised, as if prepared for a 'yuh' [j] sound) also have some frication (source.
Affrication can progress even further to become lenition, so that the 'stop' component disappears completely. In Liverpool English, this can result in 'khh' simple sounding like a sharp 'hhh' [x]. The following clip was originally found via Dialect Blog and shows the [x] appearing in Liverpool footballer Steven Gerrard's speech.
Every player is loohing (looking) forward
I have [dz] as an allophone of /d/ in my speech. I especially have it at the beginning of a syllable, not at the end. Do you have any stop-affrication? What about stop-lenition? Are there any other examples you are familiar with, cross-dialectally or cross-linguistically?