Hi Hans, this is a lighter version from sound-001.tex from your test samples: \definerenderingwindow [example] [width=0pt,height=0pt,frame=off] \setupinteraction[state=start] \useexternalrendering [mysound] [audio/x-mp3] % audio/x-mp3 [sound.mp3] %~ [embed] \definereference [StartSoundTrack] [StartRendering{mysound}] \definereference [StopSoundTrack] [StopRendering{mysound}] \definelayer[resources][width=\paperwidth,height=\paperheight] \setupbackgrounds[page][background=resources] \setupbodyfont[100pt] \starttext\bf\ss \setlayer[resources]{\placerenderingwindow[example][mysound]} \startTEXpage \button{start}[StartSoundTrack] \button{stop}[StopSoundTrack] \stopTEXpage \stoptext As reported before (https://mailman.ntg.nl/pipermail/ntg-context/2018/092327.html), sound is played fine when not embedded. But it won’t play embedded files. Without embedded sound, the relevant /Filespec reads: 7 0 obj << /F (sound.mp3) /Type /Filespec >> endobj With an embedded sound, /Filespec and /EmbeddedFile read: 7 0 obj << /Subtype /audio#2Fx-mp3 /Type /EmbeddedFile /Length 49006 >> stream endstream endobj 8 0 obj << /EF << /F 7 0 R >> /F (sound.mp3) /Type /Filespec /UF (\376\377\000s\000o\000u\000n\000d\000.\000m\000p\0003) >> endobj 10 0 obj << /EF 8 0 R /F (sound.mp3) /Type /Filespec >> endobj I don’t know why there are two /Filespec objects, since they are duplicated. In any case, the value for the /EF entry has to be a dictionary that points to the /EmbeddedFile (such as in object 8). I’m afraid that the code that generates the second /Filespec object (object 10 in the code above) is wrong. I attach a modified file fixing the issue from the PDF document generated by ConTeXt. I hope this help to fix the issue. Many thanks for your help, Pablo -- http://www.ousia.tk