Out Of Time - S6-E6
Visible crew/equipment: When the Cat becomes visible again after going through an unreality pocket, the shot changes to a wide shot of the crew. A boom mic can be seen to be pulled out of shot at the top of the screen by Kryten's head. (00:11:40)
Out Of Time - S6-E6
Visible crew/equipment: When Kryten bends down to pick up the xrays, a boom mic shadow can be seen on the top of his head. (00:05:00)
Emohawk - Polymorph II - S6-E4
Visible crew/equipment: When Rimmer says the oxy-generation unit is destroyed, a boom mic shadow can be seen on the crate in front of him. (00:09:40)
Out Of Time - S6-E6
Visible crew/equipment: In the scene just befoe Lister & the Cat go into stasis, a boom mic shadow can be seen moving on the desk in front of Rimmer. (00:12:20)
Out Of Time - S6-E6
Visible crew/equipment: When Kryten walks into the cockpit to offer Lister a beer, a boom mic can be seen at the top of the screen by Kryten's head. (00:10:05)
Emohawk - Polymorph II - S6-E4
Visible crew/equipment: After the crash when Lister comes in from outside, as he says 'it's waist high out there', a boom mic can be seen at the top of the screen. (00:09:30)
Out Of Time - S6-E6
Visible crew/equipment: At the start of the episode when Rimmer says 'any objections?' a boom mic can be seen moving across the top of the screen. (00:01:25)
Gunmen of the Apocalypse - S6-E3
Visible crew/equipment: Just after the simulant beams aboard and Lister and the Cat sit up from the table, a boom mic can be seen at the top of the screen. (00:07:40)
Gunmen of the Apocalypse - S6-E3
Visible crew/equipment: After Rimmer is sick, as Lister comes to his rescue, a boom mic shadow can be seen on the wall behind them near the horns. (00:18:50)
Gunmen of the Apocalypse - S6-E3
Visible crew/equipment: When sheriff Kryten asks for a drink, a boom mic can be seen at the top of the screen. (00:13:55)
Gunmen of the Apocalypse - S6-E3
Visible crew/equipment: At the start of the episode when Rimmer says they should surrender, a boom mic is visible at the top of the screen. (00:06:10)
Gunmen of the Apocalypse - S6-E3
Visible crew/equipment: When the crew's special skills get erased, a boom mic shadow can be seen on Lister. (00:24:20)
Answer: The cello is a large four-stringed instrument, which, when it is played, stands vertically on the floor between the player's legs (assuming they are seated). If it is to grow as large as the other instuments mentioned will, it would require a rather unseemly lack of femininity to be able to encompass it with the legs.
Rooster of Doom