Steganography is a technique that conceals the very existence of communication by means of hiding secret messages in innocuous cover objects. We previously developed a steganographic method that uses standard MIDI files (SMFs) as cover objects. Our method could conceal the secret messages in SMFs without changing their sound. We also investigated the effectiveness of our method against steganalysis. This steganalytic research revealed that files embedded using our method are vulnerable to detection, because stego SMFs lose the imprints borne by sequencers. In this study, we describe two improved methods of steganography that enable even stego SMFs to keep the sequencer's imprint. As a result, we improved the resistance of SMFs against steganalysis but there was a slight reduction in the embedding rate.