Disappearing vocals?

I came across sort of an odd problem recently (at the same time, it's kind of cool, if this had been what I was intending, if I ever found an artistic need or application for this sort of thing). I started recording vocals for a death metal project, got finished with all the tracks, did a rough mix, and bounced it. On my monitors at home, the vocals came through crystal clear. I sent an MP3 to the guy that wrote the music, and he liked what he heard. A few days later, I was going to play the track for a friend in my car. I had the mp3 on my ipod, which I play in my car using an FM Transmitter. The music starts, my first growl right before the verse comes through as it should have, and after that....NOTHING. You couldn't hear the vocals at all. Except for the slightest hint of the delay & reverb I was using, it was an instrumental track. I chalked it up to maybe I didn't mix the vocals loud enough. However, the next day, the song happened to come on my ipod when I was driving home from work, which is about 10 miles from the area I was driving in the previous day with my friend. This time, all of the vocals came through perfectly fine! I kept playing it, and noticed that as I got closer to home, the vocals started getting quieter, until I couldn't hear them at all. I tried waving my ipod around in different directions, and in certain spots, the vocals appeared again! If I held it in that spot, but made a turn, they disappeared! Does anyone know what causes this? Most of my verse vocals were single track, with some parts doubled and panned hard L&R, and the chorus doubled in the center. The verses & choruses were bussed pre-fader to a stereo aux track (volume turned all the way down on the actual tracks). On the Aux track, I set up an effects chain: Compressor to level the vocals and make them louder, then EQ, then stereo widener, that was widened just slightly. The hard panned vocals were sent to a different Aux track that was set up with the same compressor & EQ settings, but widened more with the phase inverted. Then I sent both Aux tracks Post-Fader to delay & reverb effects, which I did not turn up very much so they woulnd't be overpowering. If something I described above is causing the problem, let me know.

I am not at all sure, but this is my guess: Maybe the fm transmitter sends a mono signal to your car, and the vocals are getting phased out. Is it only when played with that adapter dealie?

Little known fact: stereo FM transmitters are pretty allergic to phase issues. I can't go into the detail but it has to do with the way the stereo information is "multiplexed" on a single carrier wave. The result is that phase issues on the stereo source can have quite dramatic effects on the transmitter, including the transmitter signal losing much of its power (!) when the signal is genuinely out-of-phase, and of course it's particularly sensitive to cancellation effects on smaller phase shift and non-mono-compatible stereo widening. I know that because that once did almost cost me my brand-new job in the advertising industry back then, the super pro studio I rented had some bad OOP wiring on the master output and my first radio commercial made the station's signal drop into the noise and we could hardly hear the commercial... it was a 15s commercial and it wasn't quite over when my phone rang... :D

Thanks for the replies! So far, yes, I have only experienced this when using the transmitter; but I haven't been actively testing in other playback scenarios. I had a feeling this might have had something to do with phase. Do either of you know where I went wrong on the mixing that caused this? Was it taking a mono track and bussing it out to a stereo auxillary? Or could it just be the stereo widener?

probably the latter. nasty tools those are.

Sounds like phase issues and (1) the car stereo was in mono. (2) the i-pod headphone lead/plug/socket is intermittently faulty. Phase issue can be fun, esp if you're playing back in mono. >

Awesome, thanks for the replies, everybody!