A very, very old approach to teaching music theory is to have students write in four vocal parts. Even though choirs aren't common today, there are important skills you can glean from this practice. The balance between instruments of a band between lead vocals, lead guitar, harmonic accompaniment (keys/guitar), bass, drums, is still 'voice leading.' Being sensitive to instrument (aka voice) intensity at different ranges, rhythmic/melodic/harmonic clarity, and overall balance is key to understanding and becoming a great composer.
