[tremendulo]

>I would expect significant causal relationships between practicing the creation of music and ability in the creation of music, and between practicing audio discrimination and ability in audio discrimination.

Yes, and real musicianship is more complicated still since hearing and playing abilities co-evolve as one cycles round and round a new piece. For example, notes previously played too quietly can be played louder merely by hearing them as louder. At least that's the way I experience it. If true it adds a whole new meaning to 'active listening' since motor activity may be included in the loop.