Sonometer, before 1752. Dr. Stephen Demainbray (1710-1782) used this instrument during his lectures to show 'the grounds on which harps, violins, harpsichords and all stringed instruments of music are constructed'. The length, tension and diameter of the strings could be altered to change the pitch of the note produced. Acoustics was considered to be part of pneumatics as it dealt with vibrations in air.