I know this topic appears here often but it seems to change every time I try to do a download.
I have a 7 year old MacBook Pro that i recently changed to OS to El Capitan after endless badgering from Apple to do so.  I previously had both XLD and Decibel on my OS for converting FLAC to Mac Compatible formats for the few downloads that I had ordered from HD Tracks.  
  I hadn't listenedto these downloads since the afore mentioned conversion.  i just ordered a new download (24 bit) from Presto Clasical and now I am getting messages that both programs will not work because they are from unknown developers.  Why these developers have become strangers to Apple after happily coexisting with them is another story but can someone tell me what the current best program for playing these files is>  My Internet search is unhelpful as everything seems to be recommending these two programs
On your MacBook, under System Preferences, Security & Privacy, General, check the settings under: Allow apps downloaded from... 

On my Macs it is set to "Mac app store and identified developers"

Updating the OS to El Capitan shouldn't have changed your previous setting but one can't be sure what may have happened in the interim.

Consider buying/using the AIFF file format for your downloads. Yes, the files are larger but require no conversion to be compatible with Mac (iTunes, right?) The cost of hard disk space has gotten relatively low. Now I buy and/or rip to AIFF in order to have maximum compatibility with present and future players. 

mahler123, when you get the message "unk developer" press the CONTROL key and try again.

Ok we are going to the Mac store today as my wife is disgusted with the performance of her 8 year old MabBook Pro since loading El Capitan.  I will ask the people there, though the drop off in Quality of the in store help over the past several years has been painful

Ok, both changing the preferences and and pressing the control key worked.  The problem now is that neither program shows up in my application file.  I downloaded XLD again, since it's free, but it isn't as it formerly did.  Now when I drag a FLAC file to the XLD icon the file Boyce's back to it's own folder.   
  Decibel wants to charge me again, and I had bought a 'lifetime '
subscription for $50 before so I didn't to use it.
  I have an Oppo 105 in the system which I use for audio only.  I bought a monitor and now I'm using the Oppo USB input to play the files.

Drag that xld icon to your application folder.o install it as an application. Then it should appear as an icon you can run as an app.
If you drag the XLD icon to the bar at the bottom of your screen it will stay there all the time. Then whenever you open Finder and drag a file down to the icon at the bottom, XLD will open and start converting. Cheers,


  I probably wasn't clear before, but I did that, the XLD icon appeared, but when I dragged a flac file into the icon, the file bounces out and returns to it's own folder.  I didn't have that issue with XLD when I used it two years ago.

Check your settings in XLD PREFERENCES>GENERAL tab and make sure you have it set to AIFF. If it's set to FLAC, it will bounce because there would be nothing to convert going from FLAC to FLAC. Cheers,
XLD works today without me having to do the above.
In the interim, I added a monitor to the system.  I have an Oppo 105 in the system but it was for audio only.  With the monitor added I can now play flac files from it's usb inputs, so now I don't think that I want to go through the hassle of converting the flac files to AIFF.
   However if I change my mind, the Oppo will play WAV, not AIFF.
If I am going to convert the files to a mac format I might as well pick
a codec that will also play on the Oppo.  What program should I use?  I've heard good things about JRiver

"Oppo will play WAV, not AIFF." That is not correct. I owned an Oppo 105 and 105D and both play AIFF fine. I did this using the digital inputs on both the front and the back with no issues. Seen many other Oppo owners do the same.  

What do you mean by "monitor"? Hardware, software? The only monitor I know of is a pair of small speakers used in a studio.

For mac music software, Audirvana+, Amarra & Pure Music are the top ones. You can trial them all & decide for yourself. JRiver was made for Windows, and just recently released for Mac to mixed reviews. I haven't heard it so no opinion. Cheers,
Give Roon a free trial. It plays flac, wav, and aiff.  


I took the Oppo data from their web site, which mentioned playing WAV and didn't mention playing AIFF.  In my experience when a component doesn't mention compatibility with a format that means it won't play that format.  I am glad to be corrected.  Actually, I added a VIDEO monitor to my OPPO, and am playing the flac files on it just fine  Problem solved, set me back $100.00 but what the hey, I'm happy

Since Apple has legal interest in AIFF and some companies don't pay any fees to Apple they get uncomfortable mentioning AIFF compatibility. Ran into that with a few portable digital players too. Cheers,