I concur with the observations of @BaronvonPurr and would like to add some more details:

Build: 119060

Affected sound: Ottomans civilization music 

Didn't seen / hear that with other civs yet. 3 full playthroughts / 28 hours playtime, so I should have appeared more frequently. Yet my system has an abundant amount of RAM for non gaming reasons.

issue 1:

The music begins to slow down, then only play some notes and keeps breaking more and more until you only can hear a scratching sound.

Sometimes it might recover and play on faster again but most of all times this did not recover and the game begins to lag heavily.

Reproducible: eventually with the attached savegame, I always needed to play 3-5 turns after the savegames for it to appear

issue 2: 

civlization music stops playing until save and load of the game then issue 1 might occour or the music stops playing again

Reproducible: eventually with the attached savegame, I always needed to play 3-5 turns after the savegames for it to appear 

issue 3:

sometimes a similar but less dramatic issue happens with ambient sound. mostly when zooming in and out the map. Less dramatic as the music does not slow down or speed up or it does not cause a laggy game, but only slightly distorted ambient sounds.

reproducible: 4/5

I will attach dxdiag and savegames. However please note what why issue 1 happens, the game has serious sound issues tabbing out to windows there are no sound issues so baronvonpurr really seems to be right that this is kind of memory exception / overflow causing this in the game only

Attachments:
msinfo32.nfo
Ottomans Turn 102.ctrdxdiag.txt

Ottomans Turn 126.ctr

1. Title: Slow performance, Turn 120
2. Description: The game is slow, FPS is around 25-30 FPS, changing resolution or quality has no effect
3. Steps to Reproduce: Load the save file
4. Reproducibility: 5/5
5. Expected Behavior: Above 60 FPS with my current PC configuration
6. Notes: I have Intel Core i7-3770K, 16GB RAM, GTX 980 Ti
7. Attachments: Save file turn 120 My game 10.ctr

Same issue here; sound (and the game overall) just keeps stuttering - and the later you go in game, the worse it gets. Might be cause it autosaves every turn?

the curious thing is that lategame is not generally affected it seems to be not a problem of which turn but rather which age (complexity and AI progress) but I had only 3 playthroughts to grasp this, so don't take it for granted. my last one I intentionally did not went to latest era. 

Glad to see so many reports on this. It would be helpful if each of you could upload a savegame and dxdiag for the devs so they might spot a common circumstance.

In fact as reported in the (remote related) thread, it helps to save the game and load. The issue did take 2-5 turns to reappear. 

I could not imagine how autosaves could causing this.