I have to make a slight correction. Crosby had the Mullin system demonstrated to him in October, 1946. By that time, Merv Griffin had been recorded. Also, the Germans recorded and played music on their radio broadcasts, which removes credit for "first commercial recording on tape" from US completely.

"...the two modified Magnetophons were used to produce the first U.S. commercial entertainment disc professionally mastered on tape, Songs by Merv Griffin, in 1946."

Crosby's investment in Ampex was essential to its success. They gave a recorder to Les Paul who promoted and endorsed the product.