Controlling greeting card music

I'm really new at this, and this idea is pretty silly, so I don't know if it's worth pursuing. Anyway, I want to take the sound circuits from a handful of musical greeting cards (you know, the birthday cards that play Tequila when you open them) and control them using the Arduino (actually, the new Japanino just released in Japan). I already determined that the circuits (which use 3 button batteries for 4.5 V) can be driven when VCC is connected to one of the digital out pins. So, I can turn the sound cards on and off that way. What I haven't decided yet is the best way to hook up multiple cards for one sound output. Because the cards always restart at the beginning of the song when turned on, I was thinking of either running the sound card outputs through the Arduino through the Analog I/O pins and select the analog in pin to sample a specific card, or just wire all of the cards to one speaker through series resistors then short the series resistor to ground for the sound cards that I want to mute via a digital pin.

The disadvantage of using the analog I/O is that it restricts the number of music cards that can be used, and I don't know what the maximum sampling rate is or how that'd affect the sound out. The disadvantage of muting the sounds by digitally shorting the music card output to ground is that I may be dropping the output signal levels from the cards as I connect each new card to the Arduino.

Has anyone tried this before? Any suggestions on the best approach?

Richard,

I want to play more than one card at a time (which is easy if I connect the battery points of each card to gnd and one of the Arduino digital pins, and then just write a 1 to each card to turn them all on at staggered intervals so they don't all have the same start times). And I want to hear only one card at a time, so I'd like to select individual cards to drive the speaker one at a time.

Thanks a lot of the help! I'm currently living in Tokyo, so I'll have to see if I can find the chip in Akihabara. I'd like to buy the breakout board and have it shipped here but it seems to be out of stock. Any idea what SparkFun's track record is on re-stocking?