If one pumped music in the form of pressurised gas perturbations emitted from speaker-shaped outlets, at an astronaut floating in space in front of them, would he hear the music through his helmet?

No. Not enough atoms in the vacuum to transmit any appreciable sound.

Ok, thanks.

Could you send a jet of a gas a short distance through the vacuum and include a (very simple) sound as a modulation in the amount ejected? What gets to the astronaut has a lot less gas - but what there is is in a series of pulses which the helmet would pick up as sound

Could you send a jet of a gas a short distance through the vacuum and include a (very simple) sound as a modulation in the amount ejected? What gets to the astronaut has a lot less gas - but what there is is in a series of pulses which the helmet would pick up as sound

 

 

Possible, I suppose but one has to consider just how quickly the gas will diffuse. For a room temperature gas, the rms speed of the molecules is quite large, around 500 m/s for N₂

Speaking of gas in outer space: how exactly will it be dispersed? Perfectly spherically? Deviated towards anything that has mass? ... ?