It is not orchestras in casual clothing, nor big screens, nor lasers or talks by the conductors, all ideas that have been tried out to increase audiences.
In fact, classical music audiences crave the simple treat that rock and light music audiences take for granted - an encore. As the late Ella Fitzgerald once sang, imploring a violin virtuoso for an encore: "Mr Paganini, don't you be a meanie ..."
For rock audiences the encore has become routine; so much so that artists return to the stage as if on automatic pilot even without the inducement of ecstatic applause. But classical concerts rarely feature encores.
They occur at the Proms at the Royal Albert Hall, and at other venues when world-famous virtuosos perform solos. But in the main, performances of symphonies end with the last movement. Indeed, it is hard to envisage how a symphony orchestra could perform an encore without simply repeating the final movement of a work.
Nevertheless, according to the survey by the South Bank Centre (SBC) and the Piper Trust, selected focus groups of classical audiences were found to resent being starved of the climactic drama of the encore.
A spokeswoman at the SBC said yesterday: "One of the things that came out is that the feeling of having an encore gives people a sense of occasion. The research confirmed that audiences want something extra.
"The feeling an encore gives is that everybody is pleased with the way the evening has gone. The orchestra are pleased and the audience are pleased, and there is an interaction between audience and orchestra. It's a unique way of an audience showing its appreciation."
At present, touring orchestras at the Royal Festival Hall give encores, the Vienna Philharmonic, when it comes, gives an encore of waltzes even after a heavyweight classical programme, and big solo artists such as the diva Jessye Norman always give encores. But at the regular symphony concerts they are unknown.
The Royal Festival Hall management will now be having talks with orchestras about introducing encores on a regular basis.
The survey also found that concert-goers can be as concerned about matters such as parking and catering as the musical programme.