TICKETS for performances by the Asian Youth Orchestra (AYO) at the Hong Kong Cultural Centre are available at Urbtix outlets. A limited number of tickets are also available at Hong Kong Record outlets. Touted by the European press as the ''best orchestra in Asia'', AYO will give concerts on August 2 and 6. The orchestra and guest soloists will be led by Rumanian conductor Sergiu Commissiona, who has won international acclaim as a dynamic conductor, known for the originality and sensitivity of his musical vision and for his rich experience. The August 2 concert will have a Shakespearean touch as the orchestra performs Tchaikovsky's ''Overture to Romeo and Juliet'', and selections from Prokofiev's ''Romeo and Juliet''. Spanish pianist Alicia de Larrocha will join the orchestra to perform Ravel's ''Concerto in G for Piano and Orchestra''. On August 6, the orchestra will perform Berlioz's ''Roman Carnival Overture'' and Dvorak's Symphony No 9 ''From the New World''. Chinese-American violin virtuoso Lin Cho-liang will join the orchestra for Tchaikovsky's ''Concerto for Violin and Orchestra''. The AYO, founded in 1987, aims to expose young musicians. to different learning opportunities.