For openSUSE Leap 15.6 standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:goupilmtos:multimedia:apps/openSUSE_Leap_15.6_standard/home:goupilmtos:multimedia:apps.repo
zypper refresh
zypper install timidity
For openSUSE Leap 15.5 standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:goupilmtos:multimedia:apps/openSUSE_Leap_15.5_standard/home:goupilmtos:multimedia:apps.repo
zypper refresh
zypper install timidity
For Goupilmtos15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:goupilmtos:multimedia:apps/Goupilmtos15.6/home:goupilmtos:multimedia:apps.repo
zypper refresh
zypper install timidity
For Goupilmtos15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:goupilmtos:multimedia:apps/Goupilmtos15.5/home:goupilmtos:multimedia:apps.repo
zypper refresh
zypper install timidity