Transmitting multiple data streams as one signal to multiple stations
Any *DMA could be used for this - CDMA, TDMA, FDMA, etc.  There are many standards that can do this sort of thing, but it is not possible to recommend a specific one without more information about these 'data streams' that you are dealing with.  

Edit: Seems like you want to work with either analog or raw samples.  With analog, you would need to transmit with N carriers, one per channel, then tune to the carrier that corresponds to the channel that you're interested in.  

For digital, generally 48 kHz @ 16 bits is a good format for audio data.  If you want to get crazy, you can do 192 kHz @ 24 bits.  48 kHz @ 16 bits is 768 kbps per audio channel.  For four channels, you would need at least 3.072 Mbit/sec.  I would recommend interleaving the channel samples and combining them into packets of some sort, then picking which samples to play at the receiver.  This could be considered sub-packet TDMA, though all of the receivers will actually have to deal with every packet.  There will be a tradeoff between packet size, latency, and overhead (due to packet headers and other synchronization necessities).  

One decent option might be wifi + some sort of audio over ethernet standard.  Take a look at Sending audio over ethernet and https://en.wikipedia.org/wiki/Audio_over_Ethernet .  Otherwise, you may find yourself building your own radios, which is a rather tall order, especially since you will need several megabits per second.