hi,

diploma in music or diploma in acoustics are two different path. diploma in music course is based on the skills which needs to become a professional artist, you may get the overview of music history, harmonics, composing etc. whether acoustics deals  with  a branch of physics which deals with wave propagation, noise control and measurement etc.

for diploma in music it basic eligibility criteria is 10+2 course passed from a recognized board of education. the course duration can be varied from 6 month to 3 years depends on institutes. I have listed down some institute name which provides this course:

Vels University (VU), Chennai

Rama Manubhai Desai College of Music and Dance (RMDCMD), Vapi

Sri Padmavati Mahila Visvavidyalayam (SPMV), Tirupati

Shaheed Udham Singh Government College (SUSGC), Sangrur

Parks-College , Tiruppur

School of Music (SM), Mumbai