We preview images attached to our mail before downloading them to our computer , Few month before Google updated preview option for AUDIO FILES from basic mode , preview of audio playing in a flash player. The preview is made with name of the AUDIO TRACK attached and name of the MAIL SENDER and DOWNLOAD option with in player.
The player is enabled with progress bar with total time and volume controls in it. The default updated flash player must be used to play AUDIO FORMATTED file in your browser. It may also play in low version players it depends upon the browsers, Here is a list of flash player version on each browser and platforms.
SEE ALSO : DOWNLOAD LINE APPLICATION FOR YOUR ANDROID
Actually audio played in Gmail is a video player in Google it also plays audio formatted(.mp3) files in it. This feature is generated form voice mail ( Google talk ) used before in Google account. Each audio player has two unique codes in them while playing audios in browser. The text marked as RED is the unique code to play audio files. where second RED text send/receive mail unique code each (send, receive,inbox,draft) mails have unique code
Check your browser on which flash player is running on >> Link Your current version information is displayed on adobe page.