If you use SIDPLAY together with old music collections which have been made especially for PlaySID on Amiga you are likely to find troublemakers among the sidtunes. You are advised to stop using such old collections. They often contain lots of wrong credits and duplicates.
If some tunes stay silent or sound strange in an undescribable manner, try toggling the PlaySID environment mode. It is a similar memory environment like PlaySID uses. It may sometimes be referred to as PlaySID compatibility mode. It is just provided to ensure compatibility even in the worst case. This mode is disabled by default, since it does not provide as flexible emulation as the native SIDPLAY mode does. It is not recommended to enable it by default, unless you really encounter some PlaySID-specific sidtunes and you know what you are doing. In modern sidtune collections you usually don't need to disable any sort of bank-switching.
Please note, that PlaySID's one-file format PSID is still the most common format used in sidtune collections. The musics in PSID format might have been converted from SIDPLAY's ASCII info file format without any loss of data. But the playback may cause problems due to a difference in PlaySID's and SIDPLAY's emulation and way of handling and initializing the music data.
PlaySID pretends plain 64 kB of C64 random-access-memory to get rid of C64-bank-switching, but does not allow the safe usage of the memory range under the SID address space. Some sidtunes use this memory for large data, e.g. samples in Chris Hülsbeck's ``Chip War'', and they sound damaged in PlaySID. The C64 uses bank-switching to map parts of the ROM and I/O address space into the limited physical address space of 64 kB. When SIDPLAY was developed from scratch, without any knowledge of PlaySID's inner workings, I decided to emulate partial bank-switching as well (although the current implementation level of SIDPLAY does not provide full support for code execution in ROM). The benefit of this decision is the ability
Attracted (or misguided?) by the plain C64 memory of PlaySID, rippers of hundreds of sidtunes totally neglected bank-switching in the changes they did to the music players. Luckily, there are only a few tunes where bank-switching would be required to successfully run them on a real C64 or SIDPLAY. Concerning the latter, the tunes just stay silent or in the worst case drop some notes or voices. For instance, Fred Gray's ``Army Moves'', ``Madballs'', ``Troll'' or Martin Galway's ``Mikie'' had been PlaySID-specific, but later were fixed to work correctly. As long as there are still PlaySID-specific sidtunes floating around in various packages on the network, you might have to temporarily enable the PlaySID environment mode to get a particular tune to work.
There is another minor problem with PlaySID-specific sidtunes that can cause sidtunes to stay silent or malfunction. We discovered some sidtunes that assume the processors' registers to contain a constant value (zero) upon initialization. Those tunes don't run on a real C64 (where the processors' registers contain the last active value, which is unlikely to be zero). Inspite of this, SIDPLAY provides the song number in all three processor registers upon song initialization. This was proposed by some users in the early development stage of SIDPLAY/DOS. In PlaySID compatibility mode SIDPLAY behaves like PlaySID and uses only the Accumulator and clears X- and Y-Register. Sub-routines should correctly initialize all the registers and addresses they use.