The show at Capital Centre last night was billed as a "Rock 'n' Roll Marathon." The billing was half right.

True, there were four groups and the concert lasted 4 1/2 hours and the energy and sound levels produced were such that the concert did strain the limits of physical endurance.

But there was very little rock 'n' roll.

What the musicians offered in its place was a motley collection of heavy metal cliches -- screaming, inarticulate guitar solos, stomping rhythms and hysterical vocals -- all of which were delivered with the subtlety of a pneumatic drill.

The sets by Angel and Mother's Finest were notable only for their relative brevity (each about 45 minutes). A reformed version of Humble Pie followed, with leader Steve Marriott howling his old songs and strutting about the stage in a manner bordering self-parody.

Frank Marino and Mahogany Rush capped the concert with a series of lackluster blues-based songs that must have had Jimi Hendrix doing a slow turn in the Great Beyond.

At one time, hard rock was a vibrant and vital musical force, practiced by imaginative artists. In the hands of last night's performers, it ceased to be music at all.