Guitarist Michael Schenker's impact upon UFO's career cannot be overestimated.

Before the German teenager's arrival (he was only 19 when he jumped ship from the Scorpions), the British rockers' early albums of half-baked space rock had been completely ignored everywhere but Japan.

But with Schenker on board, the group's sound received a well-needed attitude injection, veering toward the Anglo-hard rock style that would make them famous.

That is not to say that their first collaboration, Phenomenon, was an instant home run.

Quite the contrary, as the band seemed a tad wary of giving Schenker's more aggressive style complete freedom to roam, reining in the budding guitar hero just enough to stunt the impact of promising rockers like "Oh My and "Too Young to Know." Likewise, "Time on My Hands" and "Crystal Light" are bogged down in excessive acoustic guitars, while "Space Child" shows glimpses of their failed space rock past.

And one need only look at standout track "Doctor Doctor" for further proof of the group's uncertainties.

Later a mandatory concert staple, and still beloved as a fan favorite, the original version featured here doesn't even have what you'd call finished lyrics, and packs none of the fire eventually immortalized by the absolute monster performance captured on 1979's Strangers in the Night.

In fact, the only moment in which Phenomenon truly ignites is during the scorching "Rock Bottom," already a Schenker tour de force even here.

Ultimately, Phenomenon amply manages to hold its own, but only hints at what was still to come.