The desire to analyse the real effect of respiratory muscular training on singers led to an extensive survey at the end of 1994. Thirty professional and semi-professional singers were tested, all of them having between 2 and 20 years' experience of singing.

The test was conducted scientifically and was monitored by a ">reader at the Royal Danish Conservatoire and by a professional singer. At the end of the test, they were able to conclude:

• That the group on average had improved their inspiratory capacity by 38% compared to the start of the test
• That the average improvement in their expiratory capacity was 27%
• That the group’s compass (vocal range – particularly at the top of the range) was generally improved by 12%.
• That the men on average managed to increase their compass by a minor third.
• That the women on average managed to increase their compass by a perfect fourth.